Twilio (TWLO) 10-Q 29 Oct 20 2020 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2020	Oct. 23, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-37806
Entity Registrant Name	TWILIO INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-2574840
Entity Address, Address Line One	101 Spear Street
Entity Address, Address Line Two	First Floor
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	415
Local Phone Number	390-2337
Title of 12(b) Security	Class A Common Stock, par value $0.001 per share
Trading Symbol	TWLO
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001447669
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Common Class A
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		140,261,650
Common Class B
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		10,697,598

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 1,127,102	$ 253,660
Short-term marketable securities	2,171,602	1,599,033
Accounts receivable, net	203,835	154,067
Prepaid expenses and other current assets	66,481	54,571
Total current assets	3,569,020	2,061,331
Restricted cash	0	75
Property and equipment, net	173,279	141,256
Operating right-of-use asset	192,728	156,741
Intangible assets, net	404,422	460,849
Goodwill	2,291,616	2,296,784
Other long-term assets	92,637	33,480
Total assets	6,723,702	5,150,516
Current liabilities:
Accounts payable	39,880	39,099
Accrued expenses and other current liabilities	205,822	147,681
Deferred revenue and customer deposits	33,916	26,362
Operating lease liability, current	37,867	27,156
Finance lease liability, current	8,862	6,924
Total current liabilities	326,347	247,222
Operating lease liability, noncurrent	166,399	139,200
Finance lease liability, noncurrent	16,034	8,746
Convertible senior notes, net	432,697	458,190
Other long-term liabilities	19,957	17,747
Total liabilities	961,434	871,105
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock	0	0
Class A and Class B common stock	150	138
Additional paid-in capital	6,741,973	4,952,999
Accumulated other comprehensive income	10,585	5,086
Accumulated deficit	(990,440)	(678,812)
Total stockholders’ equity	5,762,268	4,279,411
Total liabilities and stockholders’ equity	$ 6,723,702	$ 5,150,516

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 447,969	$ 295,066	$ 1,213,686	$ 803,244
Cost of revenue	217,095	136,904	580,146	369,017
Gross profit	230,874	158,162	633,540	434,227
Operating expenses:
Research and development	136,652	104,481	371,692	281,119
Sales and marketing	140,875	100,657	387,420	262,685
General and administrative	65,617	47,690	182,038	166,409
Total operating expenses	343,144	252,828	941,150	710,213
Loss from operations	(112,270)	(94,666)	(307,610)	(275,986)
Other (expenses) income, net	(3,996)	4,377	(2,099)	2,861
Loss before (provision) benefit for income taxes	(116,266)	(90,289)	(309,709)	(273,125)
(Provision) benefit for income taxes	(648)	2,555	(1,919)	56,309
Net loss attributable to common stockholders	$ (116,914)	$ (87,734)	$ (311,628)	$ (216,816)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.79)	$ (0.64)	$ (2.18)	$ (1.70)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	147,501,075	136,400,739	142,832,021	127,506,529

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (116,914)	$ (87,734)	$ (311,628)	$ (216,816)
Other comprehensive income (loss):
Net unrealized (loss) gain on available-for-sale securities	(3,021)	1,275	5,499	3,296
Comprehensive loss attributable to common stockholders	$ (119,935)	$ (86,459)	$ (306,129)	$ (213,520)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders Equity (Unaudited) - USD ($) $ in Thousands	Total	Follow-on Public Offering	Common StockCommon Class A	Common StockCommon Class AFollow-on Public Offering	Common StockCommon Class B	Additional Paid In Capital	Additional Paid In CapitalFollow-on Public Offering	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance (in shares) at Dec. 31, 2018			80,769,763		19,310,465
Balance at Dec. 31, 2018	$ 438,235		$ 80		$ 20	$ 808,527		$ 1,282	$ (371,674)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(36,503)								(36,503)
Exercises of stock options (in shares)			748,679		1,023,984
Exercises of stock options	15,328		$ 1		$ 1	15,326
Vesting of restricted stock units (in shares)			641,406		39,360
Vesting of restricted stock units	0
Vesting of early exercised stock options	9					9
Value of equity awards withheld for tax liability (in shares)			(5,860)		(4,431)
Value of equity awards withheld for tax liability	(1,062)					(1,062)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			4,339,519		4,339,519
Conversion of shares of Class B common stock into shares of Class A common stock	0		$ 4		$ (4)	0
Shares issued (in shares)			23,555,081
Shares issued	2,658,898		$ 24			2,658,874
Net unrealized (loss) gain on available-for-sale securities	1,041							1,041
Equity awards assumed in acquisition	191,620					191,620
Stock-based compensation	59,947					59,947
Balance (in shares) at Mar. 31, 2019			110,048,588		16,029,859
Balance at Mar. 31, 2019	3,327,513		$ 109		$ 17	3,733,241		2,323	(408,177)
Balance (in shares) at Dec. 31, 2018			80,769,763		19,310,465
Balance at Dec. 31, 2018	438,235		$ 80		$ 20	808,527		1,282	(371,674)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net unrealized (loss) gain on available-for-sale securities	3,296
Balance (in shares) at Sep. 30, 2019			124,475,791		12,597,150
Balance at Sep. 30, 2019	4,284,486		$ 123		$ 14	4,868,261		4,578	(588,490)
Balance (in shares) at Dec. 31, 2018			80,769,763		19,310,465
Balance at Dec. 31, 2018	438,235		$ 80		$ 20	808,527		1,282	(371,674)
Balance (in shares) at Dec. 31, 2019			126,882,172		11,530,627
Balance at Dec. 31, 2019	4,279,411		$ 124		$ 14	4,952,999		5,086	(678,812)
Balance (in shares) at Mar. 31, 2019			110,048,588		16,029,859
Balance at Mar. 31, 2019	3,327,513		$ 109		$ 17	3,733,241		2,323	(408,177)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(92,579)								(92,579)
Exercises of stock options (in shares)			313,924		503,797
Exercises of stock options	9,927				$ 1	9,926
Vesting of restricted stock units (in shares)			675,028		29,576
Vesting of restricted stock units	1		$ 1			0
Value of equity awards withheld for tax liability (in shares)			(5,934)		(5,888)
Value of equity awards withheld for tax liability	(1,518)					(1,518)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			2,172,598		2,172,598
Conversion of shares of Class B common stock into shares of Class A common stock	0		$ 2		$ (2)
Shares issued (in shares)				8,064,515
Shares issued		$ 980,000		$ 8			$ 979,992
Costs related to the public offering	(953)					(953)
Shares issued under ESPP (in shares)			108,895
Shares issued under ESPP	8,254					8,254
Net unrealized (loss) gain on available-for-sale securities	980							980
Equity awards assumed in acquisition	(7,126)					(7,126)
Stock-based compensation	72,361					72,361
Balance (in shares) at Jun. 30, 2019			121,377,614		14,384,746
Balance at Jun. 30, 2019	4,296,860		$ 120		$ 16	4,794,177		3,303	(500,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(87,734)								(87,734)
Exercises of stock options (in shares)			231,571		351,563
Exercises of stock options	6,845				$ 0	6,845
Vesting of restricted stock units (in shares)			713,904		25,291
Vesting of restricted stock units	1		$ 1			0
Vesting of early exercised stock options	12					12
Value of equity awards withheld for tax liability (in shares)			(5,860)		(5,888)
Value of equity awards withheld for tax liability	(1,568)					(1,568)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			2,158,562		2,158,562
Conversion of shares of Class B common stock into shares of Class A common stock	0		$ 2		$ (2)
Net unrealized (loss) gain on available-for-sale securities	1,275							1,275
Equity awards assumed in acquisition	(1,940)					(1,940)
Stock-based compensation	70,735					70,735
Balance (in shares) at Sep. 30, 2019			124,475,791		12,597,150
Balance at Sep. 30, 2019	4,284,486		$ 123		$ 14	4,868,261		4,578	(588,490)
Balance (in shares) at Dec. 31, 2019			126,882,172		11,530,627
Balance at Dec. 31, 2019	4,279,411		$ 124		$ 14	4,952,999		5,086	(678,812)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(94,791)								(94,791)
Exercises of stock options (in shares)			243,029		426,001
Exercises of stock options	8,231					8,231
Vesting of restricted stock units (in shares)			849,763		23,107
Vesting of restricted stock units	1		$ 1
Value of equity awards withheld for tax liability (in shares)			(8,726)		(4,692)
Value of equity awards withheld for tax liability	(1,674)					(1,674)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			618,103		618,103
Conversion of shares of Class B common stock into shares of Class A common stock	0		$ 1		$ (1)
Donated common stock (in shares)			22,102
Donated common stock	2,701					2,701
Net unrealized (loss) gain on available-for-sale securities	(9,375)							(9,375)
Stock-based compensation	72,021					72,021
Balance (in shares) at Mar. 31, 2020			128,606,443		11,356,940
Balance at Mar. 31, 2020	4,256,525		$ 126		$ 13	5,034,278		(4,289)	(773,603)
Balance (in shares) at Dec. 31, 2019			126,882,172		11,530,627
Balance at Dec. 31, 2019	4,279,411		$ 124		$ 14	4,952,999		5,086	(678,812)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net unrealized (loss) gain on available-for-sale securities	5,499
Balance (in shares) at Sep. 30, 2020			140,173,591		10,729,264
Balance at Sep. 30, 2020	5,762,268		$ 138		$ 12	6,741,973		10,585	(990,440)
Balance (in shares) at Mar. 31, 2020			128,606,443		11,356,940
Balance at Mar. 31, 2020	4,256,525		$ 126		$ 13	5,034,278		(4,289)	(773,603)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(99,923)								(99,923)
Exercises of stock options (in shares)			1,590,891		459,010
Exercises of stock options	45,232		$ 2			45,230
Vesting of restricted stock units (in shares)			807,270		4,212
Vesting of restricted stock units	1		$ 1
Value of equity awards withheld for tax liability (in shares)			(6,018)
Value of equity awards withheld for tax liability	(1,144)					(1,144)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			983,005		983,005
Conversion of shares of Class B common stock into shares of Class A common stock	0		$ 1		$ (1)
Shares issued under ESPP (in shares)			190,642
Shares issued under ESPP	16,473					16,473
Donated common stock (in shares)			22,102
Donated common stock	3,972					3,972
Net unrealized (loss) gain on available-for-sale securities	17,895							17,895
Stock-based compensation	82,559					82,559
Balance (in shares) at Jun. 30, 2020			132,194,335		10,837,157
Balance at Jun. 30, 2020	4,321,590		$ 130		$ 12	5,181,368		13,606	(873,526)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(116,914)								(116,914)
Exercises of stock options (in shares)			218,555		173,199
Exercises of stock options	9,221					9,221
Vesting of restricted stock units (in shares)			926,032		1,688
Vesting of restricted stock units	1		$ 1
Value of equity awards withheld for tax liability (in shares)			(5,870)
Value of equity awards withheld for tax liability	(1,409)					(1,409)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)			282,780		282,780
Conversion of shares of Class B common stock into shares of Class A common stock	0
Shares issued (in shares)				5,819,838
Shares issued		$ 1,408,750		$ 6			$ 1,408,744
Costs related to the public offering	(541)					(541)
Equity component from partial settlement of 2023 convertible senior notes (in shares)			715,819
Equity component from partial settlement of 2023 convertible senior notes	46,155		$ 1			46,154
Donated common stock (in shares)			22,102
Donated common stock	5,757					5,757
Net unrealized (loss) gain on available-for-sale securities	(3,021)							(3,021)
Stock-based compensation	92,679					92,679
Balance (in shares) at Sep. 30, 2020			140,173,591		10,729,264
Balance at Sep. 30, 2020	$ 5,762,268		$ 138		$ 12	$ 6,741,973		$ 10,585	$ (990,440)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (311,628)	$ (216,816)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	98,070	79,295
Non-cash reduction to the right-of-use asset	27,240	16,732
Net amortization of investment premium and discount	2,909	(4,163)
Amortization of debt discount and issuance costs	18,432	17,689
Stock-based compensation	237,822	197,332
Amortization of deferred commissions	8,556	2,875
Tax benefit related to release of valuation allowance	(716)	(55,999)
Allowance for credit losses	8,417	1,380
Value of donated common stock	12,430	0
Other adjustments	3,013	(274)
Changes in operating assets and liabilities:
Accounts receivable	(58,340)	(27,619)
Prepaid expenses and other current assets	(8,733)	(20,743)
Other long-term assets	(64,777)	(10,756)
Accounts payable	86	4,333
Accrued expenses and other current liabilities	59,594	33,826
Deferred revenue and customer deposits	7,799	3,043
Operating lease liabilities	(25,161)	(15,397)
Long-term liabilities	2,740	(2,714)
Net cash provided by operating activities	17,753	2,024
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions, net of cash acquired, and other related payments	(2,786)	146,957
Purchases of marketable securities and other investments	(1,465,158)	(1,769,125)
Proceeds from sales and maturities of marketable securities	892,365	475,260
Capitalized software development costs	(26,114)	(16,809)
Purchases of long-lived and intangible assets	(19,252)	(18,994)
Net cash used in investing activities	(620,945)	(1,182,711)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from a public offering, net of underwriting discount and issuance costs	1,408,317	979,150
Principal payments on debt and finance leases	(6,688)	(9,327)
Proceeds from exercises of stock options and shares issued under ESPP	79,157	40,354
Value of equity awards withheld for tax liabilities	(4,227)	(4,148)
Net cash provided by financing activities	1,476,559	1,006,029
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	873,367	(174,658)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—Beginning of period	253,735	505,334
CASH, CASH EQUIVALENTS AND RESTRICTED CASH —End of period	1,127,102	330,676
Cash paid for income taxes, net	1,962	509
Cash paid for interest	1,290	1,406
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Value of common stock issued and stock awards assumed in acquisition	0	2,841,452
Value of common stock issued to settle convertible senior notes	171,840	0
Purchases of property, equipment and intangible assets, accrued but not paid	1,261	1,478
Finance lease right-of-use assets assumed in a business combination	0	14,173
Purchases of property and equipment through finance leases	15,047	3,141
Acquisition holdback	0	4,230
Stock-based compensation capitalized in software development costs	$ 10,711	$ 5,711

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Twilio Inc. (the “Company”) was incorporated in the state of Delaware on March 13, 2008. The Company is the leader in the Cloud Communications Platform category and enables developers to build, scale and operate real-time communications within their software applications via simple-to-use Application Programming Interfaces (“API”). The power, flexibility, and reliability offered by the Company’s software building blocks empower entities of virtually every shape and size to build world-class engagement into their customer experience. The Company’s headquarters are located in San Francisco, California, and the Company has subsidiaries in Australia, Bermuda, Brazil, Canada, Colombia, Czech Republic, Estonia, France, Germany, Hong Kong, India, Ireland, Japan, the Netherlands, Singapore, Spain, Sweden, the United Kingdom and the United States.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company's Annual Report on Form 10-K filed with the SEC on March 2, 2020 (“Annual Report”). The condensed consolidated balance sheet as of December 31, 2019, included herein, was derived from the audited financial statements as of that date, but may not include all disclosures including certain notes required by U.S. GAAP on an annual reporting basis. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive loss, stockholders' equity and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2020 or any future period. (b) Principles of Consolidation The condensed consolidated financial statements include the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated. (c) Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates are used for, but not limited to, revenue allowances and sales credit reserves; recoverability of long-lived and intangible assets; capitalization and useful life of the Company’s capitalized internal-use software development costs; fair value of acquired intangible assets and goodwill; accruals and contingencies. Estimates are based on historical experience and on various assumptions that the Company believes are reasonable under current circumstances. However, future events are subject to change and best estimates and judgments may require further adjustments, therefore, actual results could differ materially from those estimates. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation. (d) Concentration of Credit Risk Financial instruments that potentially expose the Company to a concentration of credit risk consist primarily of cash, cash equivalents, marketable securities and accounts receivable. The Company maintains cash, cash equivalents and marketable securities with financial institutions that management believes are financially sound and have minimal credit risk exposure although the balances will exceed insured limits. The Company sells its services to a wide variety of customers. If the financial condition or results of operations of any significant customers deteriorates substantially, operating results could be adversely affected. To reduce credit risk, management performs credit evaluations of the financial condition of significant customers. The Company does not require collateral from its credit customers and maintains reserves for estimated credit losses on customer accounts when considered necessary. Actual credit losses may differ from the Company’s estimates. During the three and nine months ended September 30, 2020 and 2019, no customer organization accounted for more than 10% of the Company’s total revenue. As of September 30, 2020, and December 31, 2019, no customer organization represented more than 10% of the Company’s gross accounts receivable. (e) Significant Accounting Policies There have been no changes to the Company's significant accounting policies as described in its Annual Report. (f) Recently Issued Accounting Guidance, Not yet Adopted In August 2020, the FASB issued ASU 2020-06, " Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40)

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial Assets The following tables provide the financial assets measured at fair value on a recurring basis: Amortized Gross Gross Fair Value Hierarchy as of September 30, 2020 Aggregate Level 1 Level 2 Level 3 Financial Assets: (In thousands) Cash and cash equivalents: Money market funds $ 999,502 $ — $ — $ 999,502 $ — $ — $ 999,502 Commercial paper 36,005 — — — 36,005 — 36,005 Total included in cash and cash equivalents 1,035,507 — — 999,502 36,005 — 1,035,507 Marketable securities: U.S. Treasury securities 222,741 704 (5) 223,440 — — 223,440 Corporate debt securities and commercial paper 1,938,664 10,212 (714) 50,000 1,898,162 — 1,948,162 Total marketable securities 2,161,405 10,916 (719) 273,440 1,898,162 — 2,171,602 Strategic investments 8,126 — — — — 8,126 8,126 Total financial assets $ 3,205,038 $ 10,916 $ (719) $ 1,272,942 $ 1,934,167 $ 8,126 $ 3,215,235 Amortized Gross Gross Fair Value Hierarchy as of December 31, 2019 Aggregate Level 1 Level 2 Level 3 Financial Assets: (In thousands) Cash and cash equivalents: Money market funds $ 153,252 $ — $ — $ 153,252 $ — $ — $ 153,252 Reverse repurchase agreements 35,800 — — — 35,800 — 35,800 Total included in cash and cash equivalents 189,052 — — 153,252 35,800 — 189,052 Marketable securities: U.S. Treasury securities 215,847 241 (3) 216,085 — — 216,085 Corporate debt securities and commercial paper 1,378,487 4,516 (55) 5,000 1,377,948 — 1,382,948 Total marketable securities 1,594,334 4,757 (58) 221,085 1,377,948 — 1,599,033 Strategic investments 5,500 — — — — 5,500 5,500 Total financial assets $ 1,788,886 $ 4,757 $ (58) $ 374,337 $ 1,413,748 $ 5,500 $ 1,793,585 The Company regularly reviews the changes to the rating of its debt securities by rating agencies as well as reasonably monitors the surrounding economic conditions to assess the risk of expected credit losses. As of September 30, 2020, the risk of expected credit losses was not significant. Interest earned on marketable securities was $7.1 million and $23.7 million in the three and nine months ended September 30, 2020, respectively, and $7.7 million and $11.8 million in the three and nine months ended September 30, 2019, respectively. The interest is recorded as other (expenses) income, net, in the accompanying condensed consolidated statements of operations. The following table summarizes the contractual maturities of marketable securities: As of September 30, 2020 As of December 31, 2019 Amortized Aggregate Amortized Aggregate Financial Assets: (In thousands) Less than one year $ 1,182,375 $ 1,186,724 $ 859,996 $ 861,181 One to three years 979,030 984,878 734,338 737,852 Total $ 2,161,405 $ 2,171,602 $ 1,594,334 $ 1,599,033 Strategic Investments The Company holds strategic investments with a fair value of $8.1 million in equity securities of privately held companies in which the Company does not have a controlling interest or significant influence. These securities are recorded as other long-term assets in the accompanying condensed consolidated balance sheets. The Company classifies its strategic investments as Level 3 within the fair value hierarchy based on the nature of inputs and judgment involved in the valuation process.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Capitalized internal-use software development costs $ 134,825 $ 100,155 Data center equipment (1) 37,255 22,009 Leasehold improvements 66,144 55,886 Office equipment 31,414 25,083 Furniture and fixtures (1) 10,602 10,095 Software 9,910 9,176 Total property and equipment 290,150 222,404 Less: accumulated depreciation and amortization (116,871) (81,148) Total property and equipment, net $ 173,279 $ 141,256 ____________________ (1) Data center equipment and furniture and fixtures contain assets under finance leases. See Note 5 for further detail.

Right-of-Use Asset and Lease Li

Right-of-Use Asset and Lease Liabilities	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Right-of-Use Asset and Lease Liabilities	Right-of-Use Asset and Lease Liabilities The Company determines if an arrangement is a lease at inception. The Company presents the operating leases in long-term assets and current and long-term liabilities. Finance lease assets are included in property and equipment, net, and finance lease liabilities are presented in current and long-term liabilities in the accompanying condensed consolidated balance sheets. Right-of-use ("ROU") assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company’s leases do not generally provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company’s lease agreements may have lease and non-lease components, which the Company accounts for as a single lease component. When estimating the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain such options will be exercised. Lease expense for lease payments is recognized on a straight-line basis over the lease term and variable payments are recognized in the period they are incurred. The Company’s lease agreements do not contain any residual value guarantees. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company has entered into various operating lease agreements for data centers and office space, and various financing leases agreements for data center and office equipment and furniture. As of September 30, 2020, the Company had 20 leased properties with remaining lease terms from less than one year to nine years, some of which include options to extend the leases for up to 5.0 years. The components of the lease expense recorded in the accompanying condensed consolidated statements of operations were as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Operating lease cost $ 12,127 $ 8,336 $ 35,048 $ 23,782 Finance lease cost: Amortization of assets 2,384 1,610 6,118 4,299 Interest on lease liabilities 212 175 604 512 Short-term lease cost 1,195 1,748 3,698 5,088 Variable lease cost 2,066 1,002 5,246 2,569 Total net lease cost $ 17,984 $ 12,871 $ 50,714 $ 36,250 As of As of September 30, December 31, Leases Classification 2020 2019 Assets: (In thousands) Operating lease assets Operating right-of-use asset, net of accumulated amortization (1) $ 192,728 $ 156,741 Finance lease assets Property and equipment, net of accumulated depreciation (2) 23,631 14,770 Total leased assets $ 216,359 $ 171,511 Liabilities: Current Operating Operating lease liability, current $ 37,867 $ 27,156 Finance Financing lease liability, current 8,862 6,924 Noncurrent Operating Operating lease liability, noncurrent 166,399 139,200 Finance Finance lease liability, noncurrent 16,034 8,746 Total lease liabilities $ 229,162 $ 182,026 ____________________ (1) Operating lease assets are recorded net of accumulated amortization of $49.6 million and $23.2 million as of September 30, 2020 and December 31, 2019, respectively. (2) Finance lease assets are recorded net of accumulated depreciation of $12.1 million and $6.0 million as of September 30, 2020 and December 31, 2019, respectively. Supplemental cash flow and other information related to leases was as follows: Nine Months Ended 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: (In thousands) Operating cash flows used in operating leases $ 34,124 $ 20,316 Operating cash flows used in finance leases (interest) $ 604 $ 491 Financing cash flows used in finance leases $ 5,721 $ 3,927 Maturities of lease liabilities were as follows: As of September 30, 2020 Operating Finance Year ended December 31, (In thousands) 2020 (remaining three months) $ 11,638 $ 2,902 2021 47,644 8,565 2022 46,478 6,242 2023 37,884 5,495 2024 33,791 2,639 Thereafter 59,892 835 Total lease payments 237,327 26,678 Less: imputed interest (33,061) (1,782) Total lease obligations 204,266 24,896 Less: current obligations (37,867) (8,862) Long-term lease obligations $ 166,399 $ 16,034 As of September 30, 2020 Operating Finance Weighted average remaining lease term (in years): 5.6 3.4 Weighted average discount rate: 5.3 % 4.1 %
Right-of-Use Asset and Lease Liabilities	Right-of-Use Asset and Lease Liabilities The Company determines if an arrangement is a lease at inception. The Company presents the operating leases in long-term assets and current and long-term liabilities. Finance lease assets are included in property and equipment, net, and finance lease liabilities are presented in current and long-term liabilities in the accompanying condensed consolidated balance sheets. Right-of-use ("ROU") assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company’s leases do not generally provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company’s lease agreements may have lease and non-lease components, which the Company accounts for as a single lease component. When estimating the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain such options will be exercised. Lease expense for lease payments is recognized on a straight-line basis over the lease term and variable payments are recognized in the period they are incurred. The Company’s lease agreements do not contain any residual value guarantees. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company has entered into various operating lease agreements for data centers and office space, and various financing leases agreements for data center and office equipment and furniture. As of September 30, 2020, the Company had 20 leased properties with remaining lease terms from less than one year to nine years, some of which include options to extend the leases for up to 5.0 years. The components of the lease expense recorded in the accompanying condensed consolidated statements of operations were as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Operating lease cost $ 12,127 $ 8,336 $ 35,048 $ 23,782 Finance lease cost: Amortization of assets 2,384 1,610 6,118 4,299 Interest on lease liabilities 212 175 604 512 Short-term lease cost 1,195 1,748 3,698 5,088 Variable lease cost 2,066 1,002 5,246 2,569 Total net lease cost $ 17,984 $ 12,871 $ 50,714 $ 36,250 As of As of September 30, December 31, Leases Classification 2020 2019 Assets: (In thousands) Operating lease assets Operating right-of-use asset, net of accumulated amortization (1) $ 192,728 $ 156,741 Finance lease assets Property and equipment, net of accumulated depreciation (2) 23,631 14,770 Total leased assets $ 216,359 $ 171,511 Liabilities: Current Operating Operating lease liability, current $ 37,867 $ 27,156 Finance Financing lease liability, current 8,862 6,924 Noncurrent Operating Operating lease liability, noncurrent 166,399 139,200 Finance Finance lease liability, noncurrent 16,034 8,746 Total lease liabilities $ 229,162 $ 182,026 ____________________ (1) Operating lease assets are recorded net of accumulated amortization of $49.6 million and $23.2 million as of September 30, 2020 and December 31, 2019, respectively. (2) Finance lease assets are recorded net of accumulated depreciation of $12.1 million and $6.0 million as of September 30, 2020 and December 31, 2019, respectively. Supplemental cash flow and other information related to leases was as follows: Nine Months Ended 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: (In thousands) Operating cash flows used in operating leases $ 34,124 $ 20,316 Operating cash flows used in finance leases (interest) $ 604 $ 491 Financing cash flows used in finance leases $ 5,721 $ 3,927 Maturities of lease liabilities were as follows: As of September 30, 2020 Operating Finance Year ended December 31, (In thousands) 2020 (remaining three months) $ 11,638 $ 2,902 2021 47,644 8,565 2022 46,478 6,242 2023 37,884 5,495 2024 33,791 2,639 Thereafter 59,892 835 Total lease payments 237,327 26,678 Less: imputed interest (33,061) (1,782) Total lease obligations 204,266 24,896 Less: current obligations (37,867) (8,862) Long-term lease obligations $ 166,399 $ 16,034 As of September 30, 2020 Operating Finance Weighted average remaining lease term (in years): 5.6 3.4 Weighted average discount rate: 5.3 % 4.1 %

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Intangible Assets Intangible assets consisted of the following: As of September 30, 2020 Gross Accumulated Net Amortizable intangible assets: (In thousands) Developed technology $ 334,599 $ (91,768) $ 242,831 Customer relationships 185,594 (47,120) 138,474 Supplier relationships 4,356 (2,692) 1,664 Trade names 20,060 (6,727) 13,333 Patent 3,247 (342) 2,905 Total amortizable intangible assets 547,856 (148,649) 399,207 Non-amortizable intangible assets: Telecommunication licenses 4,920 — 4,920 Trademarks and other 295 — 295 Total $ 553,071 $ (148,649) $ 404,422 As of December 31, 2019 Gross Accumulated Net Amortizable intangible assets: (In thousands) Developed technology $ 333,980 $ (55,390) $ 278,590 Customer relationships 182,339 (26,347) 155,992 Supplier relationships 4,356 (1,532) 2,824 Trade name 20,060 (3,727) 16,333 Patent 2,707 (262) 2,445 Total amortizable intangible assets 543,442 (87,258) 456,184 Non-amortizable intangible assets: Telecommunication licenses 4,370 — 4,370 Trademarks and other 295 — 295 Total $ 548,107 $ (87,258) $ 460,849 Total estimated future amortization expense is as follows: As of September 30, 2020 Year Ended December 31, (In thousands) 2020 (remaining three months) $ 19,919 2021 80,492 2022 77,877 2023 74,595 2024 69,316 Thereafter 77,008 Total $ 399,207

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	9 Months Ended
	Sep. 30, 2020
Accrued Liabilities and Other Liabilities [Abstract]
Accrued Expenses and Other Liabilities	Accrued Expenses and Other Liabilities Accrued expenses and other current liabilities consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Accrued payroll and related $ 35,411 $ 20,462 Accrued bonus and commission 18,218 12,898 ESPP contributions 12,223 4,023 Accrued cost of revenue 70,910 47,563 Sales and other taxes payable 33,621 34,652 Acquisition holdback 4,061 6,520 Accrued other expense 31,378 21,563 Total accrued expenses and other current liabilities $ 205,822 $ 147,681 Other long-term liabilities consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Tax liabilities $ 9,017 $ 9,268 Accrued other expenses 10,940 8,479 Total other long-term liabilities $ 19,957 $ 17,747

Notes Payable

Notes Payable	9 Months Ended
	Sep. 30, 2020
Long-term Debt, Unclassified [Abstract]
Notes Payable	Notes Payable Convertible Senior Notes and Capped Call Transactions In May 2018, the Company issued $550.0 million aggregate principal amount of 0.25% convertible senior notes due 2023 in a private placement, including $75.0 million aggregate principal amount of such Notes pursuant to the exercise in full of the over-allotment options of the initial purchasers (collectively, the “Notes”). The interest on the Notes is payable semi-annually in arrears on June 1 and December 1 of each year, beginning on December 1, 2018. The Notes may bear special interest under specified circumstances relating to the Company’s failure to comply with its reporting obligations under the indenture relating to the issuance of Notes (the “indenture”) or if the Notes are not freely tradeable as required by the indenture. The Notes will mature on June 1, 2023, unless earlier repurchased or redeemed by the Company or converted pursuant to their terms. The total net proceeds from the debt offering, after deducting initial purchaser discounts and debt issuance costs paid by us were $537.0 million. Each $1,000 principal amount of the Notes is initially convertible into 14.104 shares of the Company’s Class A common stock par value $0.001, which is equivalent to an initial conversion price of approximately $70.90 per share. The conversion rate is subject to adjustment upon the occurrence of certain specified events but will not be adjusted for any accrued and unpaid special interest. In addition, upon the occurrence of a make-whole fundamental change, as defined in the indenture, the Company will, in certain circumstances, increase the conversion rate by a number of additional shares for a holder that elects to convert its Notes in connection with such make-whole fundamental change or during the relevant redemption period. Prior to the close of business on the business day immediately preceding March 1, 2023, the Notes may be convertible at the option of the holders only under the following circumstances: (1) during any calendar quarter commencing after September 30, 2018, and only during such calendar quarter, if the last reported sale price of the Class A common stock for at least 20 trading days (whether or not consecutive) in a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is more than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business days period after any five consecutive trading day period in which, for each trading day of that period, the trading price per $1,000 principal amount of Notes for such trading day was less than 98% of the product of the last reported sale price of the Class A common stock and the conversion rate on each such trading day; (3) upon the Company’s notice that it is redeeming any or all of the Notes; or (4) upon the occurrence of specified corporate events. On or after March 1, 2023, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders of the Notes may, at their option, convert all or a portion of their Notes regardless of the foregoing conditions. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of Class A common stock, or a combination of cash and shares of Class A common stock, at the Company’s election. It is the Company’s current intent to settle the principal amount of the Notes with cash. During the three months ended September 30, 2020, the conditional conversion feature of the Notes was triggered as the last reported sale price of the Company's Class A common stock was more than or equal to 130% of the conversion price for at least 20 trading days (whether or not consecutive) in the period of 30 consecutive trading days ending on September 30, 2020 (the last trading day of the calendar quarter), and therefore the Notes are currently convertible, in whole or in part, at the option of the holders between October 1, 2020 through December 31, 2020. Whether the Notes will be convertible following such period will depend on the continued satisfaction of this condition or another conversion condition in the future. The Company continues to classify the Notes as a long-term liability in its condensed consolidated balance sheet as of September 30, 2020, based on contractual settlement provisions. The Company may redeem the Notes, in whole or in part, at its option, on or after June 1, 2021 but before the 35th scheduled trading day before the maturity date, at a cash redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any, if the last reported sale price of the Class A common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading days ending on, and including, the trading day immediately before the date the redemption notices were sent; and the trading day immediately before such notices were sent. No sinking fund is provided for the Notes. Upon the occurrence of a fundamental change (as defined in the indenture) prior to the maturity date, holders may require the Company to repurchase all or a portion of the Notes for cash at a price equal to 100% of the principal amount of the Notes to be repurchased, plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date. The Notes are senior unsecured obligations and will rank senior in right of payment to any of the Company’s indebtedness that is expressly subordinated in right of payment to the Notes; equal in right of payment with the Company’s existing and future liabilities that are not so subordinated; effectively subordinated to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) of current or future subsidiaries of the Company. The foregoing description is qualified in its entirety by reference to the text of the indenture and the form of 0.25% convertible senior notes due 2023, which were filed as exhibits to the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2018 and are incorporated herein by reference. In accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was $119.4 million and was determined by deducting the fair value of the liability component from the par value of the Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The excess of the principal amount of the liability component over its carrying amount, or the debt discount, is amortized to interest expense at an annual effective interest rate of 5.7% over the contractual terms of the Notes. In accounting for the transaction costs related to the Notes, the Company allocated the total amount incurred to the liability and equity components of the Notes based on the proportion of the proceeds allocated to the debt and equity components. Issuance costs attributable to the liability component were approximately $10.2 million, were recorded as an additional debt discount and are amortized to interest expense using the effective interest method over the contractual terms of the Notes. Issuance costs attributable to the equity component were netted with the equity component in stockholders’ equity. During the three months ended September 30, 2020, the Company settled $51.0 million aggregate principal amount of the Notes by issuing 715,819 shares of its Class A common stock and $0.9 million of cash. Of the $172.8 million total value of these transactions, $125.7 million and $47.1 million were allocated to the equity and liability components, respectively, utilizing an effective interest rate to determine the fair value of the liability component. The selected interest rate reflects the Company's incremental borrowing rate, adjusted for the Company's credit standing on nonconvertible debt with similar maturity. The extinguishment of these Notes resulted in a $3.2 million loss that is included in the other (expenses) income, net, in the accompanying condensed consolidated statement of operations. The net carrying amount of the liability component of the Notes was as follows: As of As of September 30, December 31, 2020 2019 (In thousands) Principal $ 498,988 $ 549,999 Unamortized discount (61,130) (84,647) Unamortized issuance costs (5,161) (7,162) Net carrying amount $ 432,697 $ 458,190 As of As of September 30, December 31, 2020 2019 (In thousands) Proceeds allocated to the conversion options (debt discount) $ 108,357 $ 119,435 Reacquisition of equity component upon conversion $ (114,608) $ — Issuance costs (2,819) (2,819) Net carrying amount $ (9,070) $ 116,616 Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 312 $ 344 $ 1,000 $ 1,032 Amortization of debt issuance costs 476 471 1,444 1,387 Amortization of debt discount 5,600 5,536 16,988 16,302 Total interest expense related to the Notes $ 6,388 $ 6,351 $ 19,432 $ 18,721

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	9 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Supplemental Balance Sheet Information	Supplemental Balance Sheet Information A roll-forward of the Company’s reserves is as follows: (a) Allowance for doubtful accounts: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Balance, beginning of period $ 10,248 $ 4,773 $ 6,287 $ 4,945 Additions 1,312 676 8,472 1,116 Write-offs (832) (114) (4,031) (726) Balance, end of period $ 10,728 $ 5,335 $ 10,728 $ 5,335 Percentage of revenue 2 % 2 % 1 % 1 % (b) Customer credit reserve: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Balance, beginning of period $ 11,531 $ 3,076 $ 6,784 $ 3,015 Additions 12,164 5,861 33,714 11,404 Deductions against reserve (12,915) (3,834) (29,718) (9,316) Balance, end of period $ 10,780 $ 5,103 $ 10,780 $ 5,103 Percentage of revenue 2 % 2 % 1 % 1 %

Revenue by Geographic Area

Revenue by Geographic Area	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue by Geographic Area	Revenue by Geographic Area Revenue by geographic area is based on the IP address or the mailing address at the time of registration. The following table sets forth revenue by geographic area: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Revenue by geographic area: (In thousands) United States $ 328,056 $ 210,986 $ 881,984 $ 572,537 International 119,913 84,080 331,702 230,707 Total $ 447,969 $ 295,066 $ 1,213,686 $ 803,244 Percentage of revenue by geographic area: United States 73 % 72 % 73 % 71 % International 27 % 28 % 27 % 29 % Long-lived assets outside the United States were not significant.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and ContingenciesLease and Other Commitments The Company entered into various non-cancelable operating lease agreements for its facilities with remaining lease terms from less than one year to slightly over nine years. See Note 5 to these unaudited condensed consolidated financial statements for additional detail on the Company's operating and finance lease commitments. In the three and nine months ended September 30, 2020, the Company entered into several non-cancelable vendor agreements with terms up to three years for a total purchase commitment of $28.1 million and $51.0 million, respectively. On December 1, 2016, the Company filed a patent infringement lawsuit against Telesign Corporation (“Telesign”) in the United States District Court, Northern District of California, alleging infringement of United States Patent No. 8,306,021 (“021”), United States Patent No. 8,837,465 (“465”), United States Patent No. 8,755,376 (“376”), United States Patent No. 8,736,051 (“051”), United States Patent No. 8,737,962 (“962”), United States Patent No. 9,270,833 (“833”), and United States Patent No. 9,226,217 (“217”). Telesign filed a motion to dismiss the complaint on January 25, 2017. In two orders, issued on March 31, 2017 and April 17, 2017, the court granted Telesign’s motion to dismiss with respect to the ‘962, ‘833, ‘051 and ‘217 patents, but denied Telesign’s motion to dismiss as to the ‘021, ‘465 and ‘376 patents. On August 23, 2017, Telesign petitioned the U.S. Patent and Trademark Office (“U.S. PTO”) for inter partes review of the ‘021, ‘465, and ‘376 patents. On March 9, 2018, the U.S. PTO denied Telesign’s petition for inter partes review of the ‘021 patent and granted Telesign’s petitions for inter partes review of the ‘465 and ‘376 patents. On March 6, 2019, the U.S. PTO found all challenged claims of the ‘465 and ‘376 patents unpatentable. The Company appealed the decisions to the United States Court of Appeals for the Federal Circuit who, on June 10, 2020, affirmed the U.S. PTO's rulings. The district court litigation had been stayed pending resolution of the inter partes reviews (and appeals from them). The appeals are now concluded and the district court has reopened the case and set trial on the ’021 Patent for July 2021. The Company is seeking a judgment of infringement, a judgment of willful infringement, monetary and injunctive relief, enhanced damages, and an award of costs and expenses against Telesign. In addition to the litigation discussed above, from time to time, the Company may be subject to legal actions and claims in the ordinary course of business. The Company has received, and may in the future continue to receive, claims from third parties asserting, among other things, infringement of their intellectual property rights. Future litigation may be necessary to defend the Company, its partners and its customers by determining the scope, enforceability and validity of third-party proprietary rights, or to establish our proprietary rights. The results of any current or future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors. Legal fees and other costs related to litigation and other legal proceedings are expensed as incurred and are included in general and administrative expenses in the accompanying condensed consolidated statements of operations. The Company has signed indemnification agreements with all of its board members and executive officers. The agreements indemnify the board members and executive officers from claims and expenses on actions brought against the individuals separately or jointly with the Company for certain indemnifiable events. Indemnifiable events generally mean any event or occurrence related to the fact that the board member or the executive officer was or is acting in his or her capacity as a board member or an executive officer for the Company or was or is acting or representing the interests of the Company. In the ordinary course of business and in connection with our financing and business combinations transactions, the Company enters into contractual arrangements under which it agrees to provide indemnification of varying scope and terms to business partners, customers and other parties with respect to certain matters, including, but not limited to, losses arising out of the breach of such agreements, intellectual property infringement claims made by third parties and other liabilities relating to or arising from the Company’s various products, or its acts or omissions. In these circumstances, payment may be conditional on the other party making a claim pursuant to the procedures specified in the particular contract. Further, the Company’s obligations under these agreements may be limited in terms of time and/or amount, and in some instances, the Company may have recourse against third parties for certain payments. The terms of such obligations may vary.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock As of September 30, 2020 and December 31, 2019, the Company had authorized 100,000,000 shares of preferred stock, par value $0.001, of which no shares were issued and outstanding. Common Stock As of September 30, 2020 and December 31, 2019, the Company had authorized 1,000,000,000 shares of Class A common stock and 100,000,000 shares of Class B common stock, each par value $0.001 per share. As of September 30, 2020, 140,173,591 shares of Class A common stock and 10,729,264 shares of Class B common stock were issued and outstanding. As of December 31, 2019, 126,882,172 shares of Class A common stock and 11,530,627 shares of Class B common stock were issued and outstanding. The Company had reserved shares of common stock for issuance as follows: As of As of September 30, December 31, 2020 2019 Stock options issued and outstanding 4,946,920 7,705,848 Nonvested restricted stock units issued and outstanding 8,026,189 8,490,517 Class A common stock reserved for Twilio.org 729,367 795,673 Stock-based awards available for grant under 2016 Plan 19,275,512 14,957,734 Stock-based awards available for grant under 2016 ESPP 5,042,439 3,848,953 Class A common stock reserved for the convertible senior notes 9,756,346 10,472,165 Total 47,776,773 46,270,890

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation 2008 Stock Option Plan The Company maintained a stock plan, the 2008 Stock Option Plan, as amended and restated (the “2008 Plan”), which allowed the Company to grant incentive (“ISO”), non-statutory (“NSO”) stock options and restricted stock units (“RSU”) to its employees, directors and consultants to participate in the Company’s future performance through stock-based awards at the discretion of the board of directors. Under the 2008 Plan, options to purchase the Company’s common stock could not be granted at a price less than fair value in the case of ISOs and NSOs. Fair value was determined by the board of directors, in good faith, with input from valuation consultants. On June 22, 2016, the plan was terminated in connection with the Company’s IPO. Accordingly, no shares are available for future issuance under the 2008 Plan. The 2008 Plan continues to govern outstanding equity awards granted thereunder. The Company’s right of first refusal for outstanding equity awards granted under the 2008 Plan terminated upon completion of the IPO. Options granted include provisions for early exercisability. 2016 Stock Option Plan The Company’s 2016 Stock Option and Incentive Plan (the “2016 Plan”) became effective on June 21, 2016. The 2016 Plan provides for the grant of ISOs, NSOs, restricted stock, RSUs, stock appreciation rights, unrestricted stock awards, performance share awards, dividend equivalent rights and cash-based awards to employees, directors and consultants of the Company. A total of 11,500,000 shares of the Company’s Class A common stock were initially reserved for issuance under the 2016 Plan. These available shares automatically increase each January 1, beginning on January 1, 2017, by 5% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2020 and 2019, the shares available for grant under the 2016 Plan were automatically increased by 6,920,640 and 5,004,011 shares, respectively. Under the 2016 Plan, the stock options are granted at a price per share not less than 100% of the fair market value per share of the underlying common stock on the date of grant. Under both plans, stock options generally expire 10 years from the date of grant and vest over periods determined by the board of directors. The vesting period for new-hire options and restricted stock units is generally a four year term from the date of grant, at a rate of 25% after one year, then monthly or quarterly, respectively, on a straight-line basis thereafter. In July 2017, the Company began granting restricted stock units to existing employees that vest in equal quarterly installments over a four year service period. SendGrid Equity Awards Assumed in Acquisition In connection with its acquisition of SendGrid, Inc. ("SendGrid"), the Company assumed all stock options and restricted stock units issued under SendGrid’s 2009, 2012 or 2017 Stock Incentive Plans that were outstanding on the date of acquisition. The assumed equity awards will continue to be outstanding and will be governed by the provisions of their respective plans. Additionally, the Company assumed shares of SendGrid common stock that were reserved and available for issuance under SendGrid's 2017 Equity Incentive Plan, on an as converted basis. These shares can be utilized for future equity grants under the Company’s 2016 Plan, to the extent permitted by New York Stock Exchange rules. 2016 Employee Stock Purchase Plan The Company’s Employee Stock Purchase Plan (“2016 ESPP”), as amended, initially became effective on June 21, 2016. A total of 2,400,000 shares of the Company’s Class A common stock were initially reserved for issuance under the 2016 ESPP. These available shares automatically increase each January 1, beginning on January 1, 2017, by the lesser of 1,800,000 shares of the common stock, 1% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2020 and 2019, the shares available for grant under the 2016 ESPP were automatically increased by 1,384,128 and 1,000,802 shares, respectively. The 2016 ESPP allows eligible employees to purchase shares of the Company’s Class A common stock at a discount of up to 15% through payroll deductions of their eligible compensation, subject to any plan limitations. The 2016 ESPP provides for separate six On each purchase date, eligible employees purchase the Company’s stock at a price per share equal to 85% of the lesser of (i) the fair market value of the Company’s Class A common stock on the offering date or (ii) the fair market value of the Company’s Class A common stock on the purchase date. In the three months ended September 30, 2020 and 2019, no shares of Class A common stock were purchased under the 2016 ESPP, respectively, and 103,374 shares are expected to be purchased in the fourth quarter of 2020. As of September 30, 2020, total unrecognized compensation cost related to the 2016 ESPP was $1.6 million, which will be amortized over a weighted-average period of 0.1 years. Stock Options Stock option activity under the Company's 2008 Plan and 2016 Plan as well as respective Stock Incentive Plans assumed in the SendGrid acquisition was as follows: Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2019 7,150,848 $ 28.79 6.47 $ 511,971 Granted 599,909 127.74 Exercised (3,110,685) 20.15 Forfeited and canceled (248,152) 71.27 Outstanding options as of September 30, 2020 4,391,920 $ 46.02 6.61 $ 883,089 Options vested and exercisable as of September 30, 2020 2,678,454 $ 19.05 5.54 $ 610,799 Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands, except per share amounts) Aggregate intrinsic value of stock options exercised (1) $ 89,808 $ 67,952 $ 496,198 $ 355,776 Total estimated grant date fair value of options vested $ 12,090 $ 20,959 $ 53,110 $ 62,657 Weighted-average grant date fair value per share of options granted $ — $ — $ 64.06 $ 58.16 ____________________ (1) Aggregate intrinsic value represents the difference between the fair value of the Company’s Class A common stock as reported on the New York Stock Exchange and the exercise price of outstanding “in-the-money” options. On February 28, 2017, the Company granted a total of 555,000 shares of performance-based stock options in three distinct awards to an employee with grant date fair values of $13.48, $10.26 and $8.41 per share for a total grant value of $5.9 million. The first half of each award vests upon satisfaction of a performance condition and the remainder vests thereafter in equal monthly installments over a two Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2019 555,000 $ 31.72 4.16 $ 36,941 Granted — — Exercised — — Forfeited and canceled — — Outstanding options as of September 30, 2020 555,000 $ 31.72 3.41 $ 119,530 Options vested and exercisable as of September 30, 2020 508,749 $ 31.72 3.41 $ 109,569 As of September 30, 2020, total unrecognized compensation cost related to nonvested stock options was $75.0 million, which will be amortized on a ratable basis over a weighted-average period of 2.2 years. Restricted Stock Units Number of Weighted- Aggregate Nonvested RSUs as of December 31, 2019 8,490,517 $ 74.21 $ 830,167 Granted 2,826,569 176.19 Vested (2,621,821) 70.95 Forfeited and canceled (669,076) 88.32 Nonvested RSUs as of September 30, 2020 8,026,189 $ 111.58 $ 1,979,215 As of September 30, 2020, total unrecognized compensation cost related to nonvested RSUs was $818.6 million, which will be amortized over a weighted-average period of 2.6 years. Valuation Assumptions No stock options were granted in the three months ended September 30, 2020 and 2019. The fair value of employee stock options was estimated on the date of grant using the following assumptions in the Black-Scholes option pricing model: Nine Months Ended Employee Stock Options: 2020 2019 Fair value of common stock $108.4 - $191.9 $111.3 - $130.7 Expected term (in years) 6.08 0.33 - 6.08 Expected volatility 51.9% - 56.0% 48.3% - 66.5% Risk-free interest rate 0.4% - 1.4% 2.4% - 2.5% Dividend rate —% —% Nine Months Ended Employee Stock Purchase Plan: 2020 2019 Expected term (in years) 0.50 0.50 Expected volatility 72.1% 50.3% Risk-free interest rate 0.2% 2.4% Dividend rate —% —% The following assumptions were used in the Monte Carlo simulation model to estimate the grant date fair value and the derived service period of the performance options: Asset volatility 40% Equity volatility 45% Discount rate 14% Stock price at grant date $31.7 Stock-Based Compensation Expense The Company recorded the total stock-based compensation expense as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Cost of revenue $ 2,237 $ 1,674 $ 6,217 $ 5,106 Research and development 46,294 34,348 119,344 93,388 Sales and marketing 26,573 16,143 69,602 42,456 General and administrative 14,306 16,103 42,659 56,382 Total $ 89,410 $ 68,268 $ 237,822 $ 197,332

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders Basic and diluted net loss per common share is presented in conformity with the two-class method required for participating securities. Class A and Class B common stock are the only outstanding equity in the Company. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to 10 votes per share. Shares of Class B common stock may be converted into Class A common stock at any time at the option of the stockholder and are automatically converted into Class A common stock upon sale or transfer, subject to certain limited exceptions. Basic net loss per share attributable to common stockholders is computed using the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed using the weighted-average number of common shares and, if dilutive, potential common shares outstanding during the period. The dilutive effect of these potential common shares is reflected in diluted earnings per share by application of the treasury stock method. The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net loss attributable to common stockholders (in thousands) $ (116,914) $ (87,734) $ (311,628) $ (216,816) Weighted-average shares used to compute net loss per share 147,501,075 136,400,739 142,832,021 127,506,529 Net loss per share attributable to common stockholders, basic and diluted $ (0.79) $ (0.64) $ (2.18) $ (1.70) The following outstanding shares of common stock equivalents were excluded from the calculation of the diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive: As of September 30, 2020 2019 Stock options issued and outstanding 4,946,920 8,348,766 Nonvested restricted stock units issued and outstanding 8,026,189 8,468,680 Class A common stock reserved for Twilio.org 729,367 776,334 Class A common stock committed under 2016 ESPP 103,374 99,158 Conversion spread (1) 5,013,815 3,515,621 Total 18,819,665 21,208,559 ____________________ (1) Since the Company expects to settle the principal amount of its outstanding convertible senior notes in cash and any excess in shares of the Company's Class A common stock, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The conversion spread will have a dilutive impact on diluted net income per share of Class A common stock when the average market price of the Company's Class A common stock for a given period exceeds the conversion price of $70.90 per share for the Notes. The conversion spread is calculated using the average market price of Class A common stock during the period, consistent with the treasury stock method.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded an income tax provision of $0.6 million and $1.9 million for the three and nine months ended September 30, 2020, respectively, and an income tax benefit of $2.6 million and $56.3 million for the three and nine months ended September 30, 2019, respectively. The Company continues to maintain a valuation allowance for its U.S. federal and state net deferred tax assets. The provision for income taxes recorded in the three and nine months ended September 30, 2020, consists primarily of income taxes and withholding taxes in foreign jurisdictions in which the Company conducts business. The Company's U.S. operations have been in a loss position and the Company maintains a full valuation allowance against its U.S. deferred tax assets. The tax benefit for the three and nine months ended September 30, 2019, was primarily related to a partial release of valuation allowance, of which $49.2 million was directly related to the day one impact from the acquisition of SendGrid. In connection with the SendGrid acquisition, the Company recorded a net deferred tax liability which provides an additional source of taxable income to support the realization of the pre-existing deferred tax assets. As a result, during the three and nine months ended September 30, 2019, the Company released a total of $2.5 million and $55.2 million, respectively, of its U.S. valuation allowance. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security ("CARES") Act was enacted and signed into U.S. law to provide economic relief to individuals and businesses facing economic hardship as a result of the COVID-19 pandemic. Changes in tax laws or rates are accounted for in the period of enactment. The income tax provisions of the CARES Act do not have a significant impact on the Company's current taxes, deferred taxes or uncertain tax positions. On June 7, 2019, a three-judge panel from the U.S. Court of Appeals for the Ninth Circuit overturned the U.S. Tax Court's decision in Altera Corp. v. Commissioner and upheld the portion of the Treasury regulations under Section 482 of the Internal Revenue Code that requires related parties in a cost-sharing arrangement to share expenses related to share-based compensation. As a result of this decision, the Company's gross unrecognized tax benefits increased to reflect the impact of including share-based compensation in cost-sharing arrangements. Recognizing the gross unrecognized tax benefits would not affect the Company's effective tax rate as their recognition would be offset by the reversal of the related deferred tax assets, which are subject to a full valuation allowance. On July 22, 2019, the taxpayer in the case filed a petition for a rehearing before the full Ninth Circuit and the request was denied on November 12, 2019. On February 10, 2020, the taxpayer in the case filed a petition to appeal the decision to the Supreme Court and on June 22, 2020 the Supreme Court denied the petition. There is no impact on the Company's effective tax rate for the three and nine months ended September 30, 2020 due to the full valuation allowance against its deferred tax assets. The Company will continue to monitor future developments and their potential effects on its financial statements.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On October 12, 2020, the Company entered into a definitive agreement to acquire Segment.io, Inc. (“Segment”), a cloud-based customer data platform, pursuant to an Agreement and Plan of Reorganization (the "Merger Agreement"). Upon consummation of the transactions contemplated by the Merger Agreement, all outstanding shares of Segment capital stock, vested restricted stock units, vested stock options and warrants will be cancelled in exchange for an aggregate consideration of $3.2 billion, subject to certain exceptions and adjustments, in the form of shares of Class A common stock of the Company or cash, as provided by the Merger Agreement. The Company will also assume or substitute the unvested stock options and unvested restricted stock units held by employees of Segment who remain or become employees of the Company following the closing. The proposed transaction is expected to close in the fourth quarter of 2020. The closing of this transaction is subject to certain customary closing conditions and approvals. During the nine months ended September 30, 2020, the Company incurred $0.8 million in expenses related to this transaction.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company's Annual Report on Form 10-K filed with the SEC on March 2, 2020 (“Annual Report”). The condensed consolidated balance sheet as of December 31, 2019, included herein, was derived from the audited financial statements as of that date, but may not include all disclosures including certain notes required by U.S. GAAP on an annual reporting basis. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, comprehensive loss, stockholders' equity and cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full year 2020 or any future period.
Principles of Consolidation	Principles of ConsolidationThe condensed consolidated financial statements include the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated.
Use of Estimates	Use of EstimatesThe preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. These estimates are used for, but not limited to, revenue allowances and sales credit reserves; recoverability of long-lived and intangible assets; capitalization and useful life of the Company’s capitalized internal-use software development costs; fair value of acquired intangible assets and goodwill; accruals and contingencies. Estimates are based on historical experience and on various assumptions that the Company believes are reasonable under current circumstances. However, future events are subject to change and best estimates and judgments may require further adjustments, therefore, actual results could differ materially from those estimates. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation.
Concentration of Credit Risk	Concentration of Credit RiskFinancial instruments that potentially expose the Company to a concentration of credit risk consist primarily of cash, cash equivalents, marketable securities and accounts receivable. The Company maintains cash, cash equivalents and marketable securities with financial institutions that management believes are financially sound and have minimal credit risk exposure although the balances will exceed insured limits.The Company sells its services to a wide variety of customers. If the financial condition or results of operations of any significant customers deteriorates substantially, operating results could be adversely affected. To reduce credit risk, management performs credit evaluations of the financial condition of significant customers. The Company does not require collateral from its credit customers and maintains reserves for estimated credit losses on customer accounts when considered necessary. Actual credit losses may differ from the Company’s estimates.
Recently Issued Accounting Guidance, Not yet Adopted	Recently Issued Accounting Guidance, Not yet Adopted In August 2020, the FASB issued ASU 2020-06, " Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of financial assets measured at fair value on a recurring basis	The following tables provide the financial assets measured at fair value on a recurring basis: Amortized Gross Gross Fair Value Hierarchy as of September 30, 2020 Aggregate Level 1 Level 2 Level 3 Financial Assets: (In thousands) Cash and cash equivalents: Money market funds $ 999,502 $ — $ — $ 999,502 $ — $ — $ 999,502 Commercial paper 36,005 — — — 36,005 — 36,005 Total included in cash and cash equivalents 1,035,507 — — 999,502 36,005 — 1,035,507 Marketable securities: U.S. Treasury securities 222,741 704 (5) 223,440 — — 223,440 Corporate debt securities and commercial paper 1,938,664 10,212 (714) 50,000 1,898,162 — 1,948,162 Total marketable securities 2,161,405 10,916 (719) 273,440 1,898,162 — 2,171,602 Strategic investments 8,126 — — — — 8,126 8,126 Total financial assets $ 3,205,038 $ 10,916 $ (719) $ 1,272,942 $ 1,934,167 $ 8,126 $ 3,215,235 Amortized Gross Gross Fair Value Hierarchy as of December 31, 2019 Aggregate Level 1 Level 2 Level 3 Financial Assets: (In thousands) Cash and cash equivalents: Money market funds $ 153,252 $ — $ — $ 153,252 $ — $ — $ 153,252 Reverse repurchase agreements 35,800 — — — 35,800 — 35,800 Total included in cash and cash equivalents 189,052 — — 153,252 35,800 — 189,052 Marketable securities: U.S. Treasury securities 215,847 241 (3) 216,085 — — 216,085 Corporate debt securities and commercial paper 1,378,487 4,516 (55) 5,000 1,377,948 — 1,382,948 Total marketable securities 1,594,334 4,757 (58) 221,085 1,377,948 — 1,599,033 Strategic investments 5,500 — — — — 5,500 5,500 Total financial assets $ 1,788,886 $ 4,757 $ (58) $ 374,337 $ 1,413,748 $ 5,500 $ 1,793,585
Schedule of contractual maturities of marketable securities	The following table summarizes the contractual maturities of marketable securities: As of September 30, 2020 As of December 31, 2019 Amortized Aggregate Amortized Aggregate Financial Assets: (In thousands) Less than one year $ 1,182,375 $ 1,186,724 $ 859,996 $ 861,181 One to three years 979,030 984,878 734,338 737,852 Total $ 2,161,405 $ 2,171,602 $ 1,594,334 $ 1,599,033

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Property and equipment consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Capitalized internal-use software development costs $ 134,825 $ 100,155 Data center equipment (1) 37,255 22,009 Leasehold improvements 66,144 55,886 Office equipment 31,414 25,083 Furniture and fixtures (1) 10,602 10,095 Software 9,910 9,176 Total property and equipment 290,150 222,404 Less: accumulated depreciation and amortization (116,871) (81,148) Total property and equipment, net $ 173,279 $ 141,256 ____________________ (1) Data center equipment and furniture and fixtures contain assets under finance leases. See Note 5 for further detail.

Right-of-Use Asset and Lease _2

Right-of-Use Asset and Lease Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Lease, Cost	The components of the lease expense recorded in the accompanying condensed consolidated statements of operations were as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Operating lease cost $ 12,127 $ 8,336 $ 35,048 $ 23,782 Finance lease cost: Amortization of assets 2,384 1,610 6,118 4,299 Interest on lease liabilities 212 175 604 512 Short-term lease cost 1,195 1,748 3,698 5,088 Variable lease cost 2,066 1,002 5,246 2,569 Total net lease cost $ 17,984 $ 12,871 $ 50,714 $ 36,250 Supplemental cash flow and other information related to leases was as follows: Nine Months Ended 2020 2019 Cash paid for amounts included in the measurement of lease liabilities: (In thousands) Operating cash flows used in operating leases $ 34,124 $ 20,316 Operating cash flows used in finance leases (interest) $ 604 $ 491 Financing cash flows used in finance leases $ 5,721 $ 3,927 As of September 30, 2020 Operating Finance Weighted average remaining lease term (in years): 5.6 3.4 Weighted average discount rate: 5.3 % 4.1 %
Assets and Liabilities, Lessee	Supplemental balance sheet information related to leases was as follows: As of As of September 30, December 31, Leases Classification 2020 2019 Assets: (In thousands) Operating lease assets Operating right-of-use asset, net of accumulated amortization (1) $ 192,728 $ 156,741 Finance lease assets Property and equipment, net of accumulated depreciation (2) 23,631 14,770 Total leased assets $ 216,359 $ 171,511 Liabilities: Current Operating Operating lease liability, current $ 37,867 $ 27,156 Finance Financing lease liability, current 8,862 6,924 Noncurrent Operating Operating lease liability, noncurrent 166,399 139,200 Finance Finance lease liability, noncurrent 16,034 8,746 Total lease liabilities $ 229,162 $ 182,026 ____________________ (1) Operating lease assets are recorded net of accumulated amortization of $49.6 million and $23.2 million as of September 30, 2020 and December 31, 2019, respectively. (2) Finance lease assets are recorded net of accumulated depreciation of $12.1 million and $6.0 million as of September 30, 2020 and December 31, 2019, respectively.
Lessee, Operating Lease, Liability, Maturity	Maturities of lease liabilities were as follows: As of September 30, 2020 Operating Finance Year ended December 31, (In thousands) 2020 (remaining three months) $ 11,638 $ 2,902 2021 47,644 8,565 2022 46,478 6,242 2023 37,884 5,495 2024 33,791 2,639 Thereafter 59,892 835 Total lease payments 237,327 26,678 Less: imputed interest (33,061) (1,782) Total lease obligations 204,266 24,896 Less: current obligations (37,867) (8,862) Long-term lease obligations $ 166,399 $ 16,034
Finance Lease, Liability, Maturity	Maturities of lease liabilities were as follows: As of September 30, 2020 Operating Finance Year ended December 31, (In thousands) 2020 (remaining three months) $ 11,638 $ 2,902 2021 47,644 8,565 2022 46,478 6,242 2023 37,884 5,495 2024 33,791 2,639 Thereafter 59,892 835 Total lease payments 237,327 26,678 Less: imputed interest (33,061) (1,782) Total lease obligations 204,266 24,896 Less: current obligations (37,867) (8,862) Long-term lease obligations $ 166,399 $ 16,034

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	Intangible assets consisted of the following: As of September 30, 2020 Gross Accumulated Net Amortizable intangible assets: (In thousands) Developed technology $ 334,599 $ (91,768) $ 242,831 Customer relationships 185,594 (47,120) 138,474 Supplier relationships 4,356 (2,692) 1,664 Trade names 20,060 (6,727) 13,333 Patent 3,247 (342) 2,905 Total amortizable intangible assets 547,856 (148,649) 399,207 Non-amortizable intangible assets: Telecommunication licenses 4,920 — 4,920 Trademarks and other 295 — 295 Total $ 553,071 $ (148,649) $ 404,422 As of December 31, 2019 Gross Accumulated Net Amortizable intangible assets: (In thousands) Developed technology $ 333,980 $ (55,390) $ 278,590 Customer relationships 182,339 (26,347) 155,992 Supplier relationships 4,356 (1,532) 2,824 Trade name 20,060 (3,727) 16,333 Patent 2,707 (262) 2,445 Total amortizable intangible assets 543,442 (87,258) 456,184 Non-amortizable intangible assets: Telecommunication licenses 4,370 — 4,370 Trademarks and other 295 — 295 Total $ 548,107 $ (87,258) $ 460,849
Schedule of total estimated future amortization expense	Total estimated future amortization expense is as follows: As of September 30, 2020 Year Ended December 31, (In thousands) 2020 (remaining three months) $ 19,919 2021 80,492 2022 77,877 2023 74,595 2024 69,316 Thereafter 77,008 Total $ 399,207

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued Liabilities and Other Liabilities [Abstract]
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Accrued payroll and related $ 35,411 $ 20,462 Accrued bonus and commission 18,218 12,898 ESPP contributions 12,223 4,023 Accrued cost of revenue 70,910 47,563 Sales and other taxes payable 33,621 34,652 Acquisition holdback 4,061 6,520 Accrued other expense 31,378 21,563 Total accrued expenses and other current liabilities $ 205,822 $ 147,681
Schedule of other long-term liabilities	Other long-term liabilities consisted of the following: As of As of September 30, December 31, 2020 2019 (In thousands) Tax liabilities $ 9,017 $ 9,268 Accrued other expenses 10,940 8,479 Total other long-term liabilities $ 19,957 $ 17,747

Notes Payable (Tables)

Notes Payable (Tables)	9 Months Ended
	Sep. 30, 2020
Long-term Debt, Unclassified [Abstract]
Schedule of net carrying amount of the liability and equity components of the Notes	The net carrying amount of the liability component of the Notes was as follows: As of As of September 30, December 31, 2020 2019 (In thousands) Principal $ 498,988 $ 549,999 Unamortized discount (61,130) (84,647) Unamortized issuance costs (5,161) (7,162) Net carrying amount $ 432,697 $ 458,190 As of As of September 30, December 31, 2020 2019 (In thousands) Proceeds allocated to the conversion options (debt discount) $ 108,357 $ 119,435 Reacquisition of equity component upon conversion $ (114,608) $ — Issuance costs (2,819) (2,819) Net carrying amount $ (9,070) $ 116,616
Schedule of interest expense recognized related to the Notes	The following table sets forth the interest expense recognized related to the Notes: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Contractual interest expense $ 312 $ 344 $ 1,000 $ 1,032 Amortization of debt issuance costs 476 471 1,444 1,387 Amortization of debt discount 5,600 5,536 16,988 16,302 Total interest expense related to the Notes $ 6,388 $ 6,351 $ 19,432 $ 18,721

Supplemental Balance Sheet In_2

Supplemental Balance Sheet Information (Tables)	9 Months Ended
	Sep. 30, 2020
Receivables [Abstract]
Schedule of the allowance for doubtful accounts	Allowance for doubtful accounts: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Balance, beginning of period $ 10,248 $ 4,773 $ 6,287 $ 4,945 Additions 1,312 676 8,472 1,116 Write-offs (832) (114) (4,031) (726) Balance, end of period $ 10,728 $ 5,335 $ 10,728 $ 5,335 Percentage of revenue 2 % 2 % 1 % 1 %
Schedule of the sales credit reserve	Customer credit reserve: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Balance, beginning of period $ 11,531 $ 3,076 $ 6,784 $ 3,015 Additions 12,164 5,861 33,714 11,404 Deductions against reserve (12,915) (3,834) (29,718) (9,316) Balance, end of period $ 10,780 $ 5,103 $ 10,780 $ 5,103 Percentage of revenue 2 % 2 % 1 % 1 %

Revenue by Geographic Area (Tab

Revenue by Geographic Area (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Schedule of revenue by geographic area	Revenue by geographic area is based on the IP address or the mailing address at the time of registration. The following table sets forth revenue by geographic area: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Revenue by geographic area: (In thousands) United States $ 328,056 $ 210,986 $ 881,984 $ 572,537 International 119,913 84,080 331,702 230,707 Total $ 447,969 $ 295,066 $ 1,213,686 $ 803,244 Percentage of revenue by geographic area: United States 73 % 72 % 73 % 71 % International 27 % 28 % 27 % 29 %

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity Note [Abstract]
Schedule of reserved shares of common stock for issuance	The Company had reserved shares of common stock for issuance as follows: As of As of September 30, December 31, 2020 2019 Stock options issued and outstanding 4,946,920 7,705,848 Nonvested restricted stock units issued and outstanding 8,026,189 8,490,517 Class A common stock reserved for Twilio.org 729,367 795,673 Stock-based awards available for grant under 2016 Plan 19,275,512 14,957,734 Stock-based awards available for grant under 2016 ESPP 5,042,439 3,848,953 Class A common stock reserved for the convertible senior notes 9,756,346 10,472,165 Total 47,776,773 46,270,890

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of stock options activity	Stock option activity under the Company's 2008 Plan and 2016 Plan as well as respective Stock Incentive Plans assumed in the SendGrid acquisition was as follows: Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2019 7,150,848 $ 28.79 6.47 $ 511,971 Granted 599,909 127.74 Exercised (3,110,685) 20.15 Forfeited and canceled (248,152) 71.27 Outstanding options as of September 30, 2020 4,391,920 $ 46.02 6.61 $ 883,089 Options vested and exercisable as of September 30, 2020 2,678,454 $ 19.05 5.54 $ 610,799 Number of Weighted- Weighted- Aggregate Outstanding options as of December 31, 2019 555,000 $ 31.72 4.16 $ 36,941 Granted — — Exercised — — Forfeited and canceled — — Outstanding options as of September 30, 2020 555,000 $ 31.72 3.41 $ 119,530 Options vested and exercisable as of September 30, 2020 508,749 $ 31.72 3.41 $ 109,569
Schedule of weighted average grant date fair value	Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands, except per share amounts) Aggregate intrinsic value of stock options exercised (1) $ 89,808 $ 67,952 $ 496,198 $ 355,776 Total estimated grant date fair value of options vested $ 12,090 $ 20,959 $ 53,110 $ 62,657 Weighted-average grant date fair value per share of options granted $ — $ — $ 64.06 $ 58.16 ____________________ (1) Aggregate intrinsic value represents the difference between the fair value of the Company’s Class A common stock as reported on the New York Stock Exchange and the exercise price of outstanding “in-the-money” options.
Schedule of restricted stock unit activity	Number of Weighted- Aggregate Nonvested RSUs as of December 31, 2019 8,490,517 $ 74.21 $ 830,167 Granted 2,826,569 176.19 Vested (2,621,821) 70.95 Forfeited and canceled (669,076) 88.32 Nonvested RSUs as of September 30, 2020 8,026,189 $ 111.58 $ 1,979,215
Schedule of valuation assumptions, options	The fair value of employee stock options was estimated on the date of grant using the following assumptions in the Black-Scholes option pricing model: Nine Months Ended Employee Stock Options: 2020 2019 Fair value of common stock $108.4 - $191.9 $111.3 - $130.7 Expected term (in years) 6.08 0.33 - 6.08 Expected volatility 51.9% - 56.0% 48.3% - 66.5% Risk-free interest rate 0.4% - 1.4% 2.4% - 2.5% Dividend rate —% —% Nine Months Ended Employee Stock Purchase Plan: 2020 2019 Expected term (in years) 0.50 0.50 Expected volatility 72.1% 50.3% Risk-free interest rate 0.2% 2.4% Dividend rate —% —% The following assumptions were used in the Monte Carlo simulation model to estimate the grant date fair value and the derived service period of the performance options: Asset volatility 40% Equity volatility 45% Discount rate 14% Stock price at grant date $31.7
Schedule of stock based compensation expense	The Company recorded the total stock-based compensation expense as follows: Three Months Ended Nine Months Ended 2020 2019 2020 2019 (In thousands) Cost of revenue $ 2,237 $ 1,674 $ 6,217 $ 5,106 Research and development 46,294 34,348 119,344 93,388 Sales and marketing 26,573 16,143 69,602 42,456 General and administrative 14,306 16,103 42,659 56,382 Total $ 89,410 $ 68,268 $ 237,822 $ 197,332

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of the calculation of basic and diluted net loss per share attributable to common stockholders	The following table sets forth the calculation of basic and diluted net loss per share attributable to common stockholders during the periods presented: Three Months Ended Nine Months Ended 2020 2019 2020 2019 Net loss attributable to common stockholders (in thousands) $ (116,914) $ (87,734) $ (311,628) $ (216,816) Weighted-average shares used to compute net loss per share 147,501,075 136,400,739 142,832,021 127,506,529 Net loss per share attributable to common stockholders, basic and diluted $ (0.79) $ (0.64) $ (2.18) $ (1.70)
Schedule of common stock equivalents excluded from the computation of the diluted net loss per share attributable to common stockholders	The following outstanding shares of common stock equivalents were excluded from the calculation of the diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive: As of September 30, 2020 2019 Stock options issued and outstanding 4,946,920 8,348,766 Nonvested restricted stock units issued and outstanding 8,026,189 8,468,680 Class A common stock reserved for Twilio.org 729,367 776,334 Class A common stock committed under 2016 ESPP 103,374 99,158 Conversion spread (1) 5,013,815 3,515,621 Total 18,819,665 21,208,559 ____________________ (1) Since the Company expects to settle the principal amount of its outstanding convertible senior notes in cash and any excess in shares of the Company's Class A common stock, the Company uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The conversion spread will have a dilutive impact on diluted net income per share of Class A common stock when the average market price of the Company's Class A common stock for a given period exceeds the conversion price of $70.90 per share for the Notes. The conversion spread is calculated using the average market price of Class A common stock during the period, consistent with the treasury stock method.

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Measurements, Financial Assets
Total amortized cost	$ 2,161,405	$ 1,594,334
Marketable securities, accumulated gross unrealized gain, before tax	10,916	4,757
Marketable securities, gross unrealized losses less than 12 months	(719)	(58)
Marketable securities, aggregate fair value	2,171,602	1,599,033
Strategic investments	8,100
Strategic investments, gross unrealized gains	0	0
Strategic investments, gross unrealized losses	0	0
Strategic investments	8,126	5,500
Total gross unrealized gains	10,916	4,757
Total gross unrealized losses	(719)	(58)
Total financial assets	3,215,235	1,793,585
U.S. Treasury securities
Fair Value Measurements, Financial Assets
Marketable securities, accumulated gross unrealized gain, before tax	704	241
Marketable securities, gross unrealized losses less than 12 months	(5)	(3)
Marketable securities, aggregate fair value	223,440	216,085
Corporate debt securities and commercial paper
Fair Value Measurements, Financial Assets
Marketable securities, accumulated gross unrealized gain, before tax	10,212	4,516
Marketable securities, gross unrealized losses less than 12 months	(714)	(55)
Marketable securities, aggregate fair value	1,948,162	1,382,948
Level 1
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	273,440	221,085
Strategic investments	0	0
Total financial assets	1,272,942	374,337
Level 1 | U.S. Treasury securities
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	223,440	216,085
Level 1 | Corporate debt securities and commercial paper
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	50,000	5,000
Level 2
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	1,898,162	1,377,948
Strategic investments	0	0
Total financial assets	1,934,167	1,413,748
Level 2 | U.S. Treasury securities
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	0	0
Level 2 | Corporate debt securities and commercial paper
Fair Value Measurements, Financial Assets
Marketable securities, aggregate fair value	1,898,162	1,377,948
Level 3
Fair Value Measurements, Financial Assets
Strategic investments	8,126	5,500
Total financial assets	8,126	5,500
Carrying Value
Fair Value Measurements, Financial Assets
Cash and cash equivalents	1,035,507	189,052
Total amortized cost	2,161,405	1,594,334
Strategic investments	8,126	5,500
Total financial assets, amortized cost or carrying value	3,205,038	1,788,886
Carrying Value | U.S. Treasury securities
Fair Value Measurements, Financial Assets
Total amortized cost	222,741	215,847
Carrying Value | Corporate debt securities and commercial paper
Fair Value Measurements, Financial Assets
Total amortized cost	1,938,664	1,378,487
Carrying Value | Money market funds
Fair Value Measurements, Financial Assets
Cash and cash equivalents	999,502	153,252
Carrying Value | Commercial paper
Fair Value Measurements, Financial Assets
Cash and cash equivalents	36,005
Carrying Value | Reverse repurchase agreements
Fair Value Measurements, Financial Assets
Cash and cash equivalents		35,800
Aggregate Fair Value
Fair Value Measurements, Financial Assets
Cash and cash equivalents	1,035,507	189,052
Marketable securities, aggregate fair value	2,171,602	1,599,033
Aggregate Fair Value | Money market funds
Fair Value Measurements, Financial Assets
Cash and cash equivalents	999,502	153,252
Aggregate Fair Value | Commercial paper
Fair Value Measurements, Financial Assets
Cash and cash equivalents	36,005
Aggregate Fair Value | Reverse repurchase agreements
Fair Value Measurements, Financial Assets
Cash and cash equivalents		35,800
Aggregate Fair Value | Level 1
Fair Value Measurements, Financial Assets
Cash and cash equivalents	999,502	153,252
Aggregate Fair Value | Level 1 | Money market funds
Fair Value Measurements, Financial Assets
Cash and cash equivalents	999,502	153,252
Aggregate Fair Value | Level 1 | Reverse repurchase agreements
Fair Value Measurements, Financial Assets
Cash and cash equivalents		0
Aggregate Fair Value | Level 2
Fair Value Measurements, Financial Assets
Cash and cash equivalents	36,005	35,800
Aggregate Fair Value | Level 2 | Money market funds
Fair Value Measurements, Financial Assets
Cash and cash equivalents	0	0
Aggregate Fair Value | Level 2 | Commercial paper
Fair Value Measurements, Financial Assets
Cash and cash equivalents	$ 36,005
Aggregate Fair Value | Level 2 | Reverse repurchase agreements
Fair Value Measurements, Financial Assets
Cash and cash equivalents		$ 35,800

Fair Value Measurements - Marke

Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Marketable Securities
Interest earned on marketable securities	$ 7.1	$ 7.7	$ 23.7	$ 11.8
Other long-term investments	$ 8.1		$ 8.1

Fair Value Measurements - Contr

Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than one year, amortized cost	$ 1,182,375	$ 859,996
One to three years, amortized cost	979,030	734,338
Total amortized cost	2,161,405	1,594,334
Total aggregate fair value	2,171,602	1,599,033
Aggregate Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Less than one year, aggregate fair value	1,186,724	861,181
One to three years, aggregate fair value	984,878	737,852
Total aggregate fair value	$ 2,171,602	$ 1,599,033

Fair Value Measurements - Conve

Fair Value Measurements - Convertible Senior Notes (Details) - Convertible senior notes, 0.25%, due 2023 - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	May 31, 2018
Fair Value Measurements, Liabilities
Interest rate (as a percent)			0.25%
Level 2
Fair Value Measurements, Liabilities
Fair value of the notes	$ 1,731.3	$ 841.3

Property and Equipment - Proper

Property and Equipment - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property and Equipment
Total property and equipment	$ 290,150	$ 222,404
Less: accumulated depreciation and amortization	(116,871)	(81,148)
Total property and equipment, net	173,279	141,256
Capitalized internal-use software development costs
Property and Equipment
Total property and equipment	134,825	100,155
Data center equipment
Property and Equipment
Total property and equipment	37,255	22,009
Leasehold improvements
Property and Equipment
Total property and equipment	66,144	55,886
Office equipment
Property and Equipment
Total property and equipment	31,414	25,083
Furniture and fixtures
Property and Equipment
Total property and equipment	10,602	10,095
Software
Property and Equipment
Total property and equipment	$ 9,910	$ 9,176

Property and Equipment - Capita

Property and Equipment - Capitalized Software Development Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Capitalized internal use software development costs	$ 12,200	$ 8,800	$ 36,800	$ 22,500
Stock-based compensation capitalized in software development costs	3,700	2,500	10,711	5,711
Amortization of capitalized software development costs	$ 4,400	$ 4,400	$ 13,400	$ 12,500

Right-of-Use Asset and Lease _3

Right-of-Use Asset and Lease Liabilities - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)property
Lessee, Lease, Description [Line Items]
Number of leased properties | property	20
Renewal option	5 years
Operating lease, not yet commenced, obligation	$ 8.2
Operating lease, not yet commenced, lease term	7 years 1 month 6 days
Finance lease, not yet commenced, obligation	$ 4.1
Finance lease, not yet commenced, lease term	4 years
Minimum
Lessee, Lease, Description [Line Items]
Term of lease	1 year
Maximum
Lessee, Lease, Description [Line Items]
Term of lease	9 years

Right-of-Use Asset and Lease _4

Right-of-Use Asset and Lease Liabilities - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 12,127	$ 8,336	$ 35,048	$ 23,782
Finance lease cost:
Amortization of assets	2,384	1,610	6,118	4,299
Interest on lease liabilities	212	175	604	512
Short-term lease cost	1,195	1,748	3,698	5,088
Variable lease cost	2,066	1,002	5,246	2,569
Total net lease cost	$ 17,984	$ 12,871	$ 50,714	$ 36,250

Right-of-Use Asset and Lease _5

Right-of-Use Asset and Lease Liabilities - Balance Sheet Classification of Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Operating lease assets	$ 192,728	$ 156,741
Finance lease assets	23,631	14,770
Total leased assets	216,359	171,511
Current liabilities:
Operating	37,867	27,156
Finance	8,862	6,924
Noncurrent liabilities
Operating	166,399	139,200
Finance	16,034	8,746
Total lease liabilities	229,162	182,026
Operating lease accumulated amortization	49,600	23,200
Finance lease accumulated amortization	$ 12,100	$ 6,000
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization

Right-of-Use Asset and Lease _6

Right-of-Use Asset and Lease Liabilities - Supplemental Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$ 34,124	$ 20,316
Operating cash flows used in finance leases (interest)	604	491
Financing cash flows used in finance leases	$ 5,721	$ 3,927
Weighted Average Remaining Lease Term [Abstract]
Operating leases	5 years 7 months 6 days
Finance leases	3 years 4 months 24 days
Weighted Average Discount Rate [Abstract]
Operating leases	5.30%
Finance leases	4.10%

Right-of-Use Asset and Lease _7

Right-of-Use Asset and Lease Liabilities - Lease Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Maturity Of Operating Lease Liabilities
2020	$ 11,638
2021	47,644
2022	46,478
2023	37,884
2024	33,791
Thereafter	59,892
Total lease payments	237,327
Less: imputed interest	(33,061)
Total lease obligations	204,266
Less: current obligations	(37,867)	$ (27,156)
Long-term lease obligations	166,399	139,200
Maturity Of Finance Lease Liabilities
2020	2,902
2021	8,565
2022	6,242
2023	5,495
2024	2,639
Thereafter	835
Total lease payments	26,678
Less: imputed interest	(1,782)
Total lease obligations	24,896
Less: current obligations	(8,862)	(6,924)
Long-term lease obligations	$ 16,034	$ 8,746

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortizable intangible assets:
Gross	$ 547,856	$ 543,442
Accumulated Amortization	(148,649)	(87,258)
Net	399,207	456,184
Intangible assets, gross	553,071	548,107
Total	404,422	460,849
Telecommunication licenses
Amortizable intangible assets:
Non-amortizable intangible assets:	4,920	4,370
Trademarks and other
Amortizable intangible assets:
Non-amortizable intangible assets:	295	295
Developed technology
Amortizable intangible assets:
Gross	334,599	333,980
Accumulated Amortization	(91,768)	(55,390)
Net	242,831	278,590
Customer relationships
Amortizable intangible assets:
Gross	185,594	182,339
Accumulated Amortization	(47,120)	(26,347)
Net	138,474	155,992
Supplier relationships
Amortizable intangible assets:
Gross	4,356	4,356
Accumulated Amortization	(2,692)	(1,532)
Net	1,664	2,824
Trade names
Amortizable intangible assets:
Gross	20,060	20,060
Accumulated Amortization	(6,727)	(3,727)
Net	13,333	16,333
Patent
Amortizable intangible assets:
Gross	3,247	2,707
Accumulated Amortization	(342)	(262)
Net	$ 2,905	$ 2,445

Intangible Assets - Amortizatio

Intangible Assets - Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 20.4	$ 20	$ 61.3	$ 52.9

Intangible Assets - Total Estim

Intangible Assets - Total Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Intangible Assets
2020 (remaining three months)	$ 19,919
2021	80,492
2022	77,877
2023	74,595
2024	69,316
Thereafter	77,008
Net	$ 399,207	$ 456,184

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities - Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities and Other Liabilities [Abstract]
Accrued payroll and related	$ 35,411	$ 20,462
Accrued bonus and commission	18,218	12,898
ESPP contributions	12,223	4,023
Accrued cost of revenue	70,910	47,563
Sales and other taxes payable	33,621	34,652
Acquisition holdback	4,061	6,520
Accrued other expense	31,378	21,563
Total accrued expenses and other current liabilities	$ 205,822	$ 147,681

Accrued Expenses and Other Li_4

Accrued Expenses and Other Liabilities - Long-term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities and Other Liabilities [Abstract]
Tax liabilities	$ 9,017	$ 9,268
Accrued other expenses	10,940	8,479
Total other long-term liabilities	$ 19,957	$ 17,747

Notes Payable - Issuance (Detai

Notes Payable - Issuance (Details) - USD ($)	1 Months Ended
	May 31, 2018	Sep. 30, 2020	Dec. 31, 2019
Convertible senior notes, 0.25%, due 2023
Debt Instrument [Line Items]
Principal	$ 550,000,000	$ 498,988,000	$ 549,999,000
Interest rate (as a percent)	0.25%
Net proceeds from the debt offering	$ 537,000,000
Convertible senior notes, 0.25%, due 2023 - over-allotment
Debt Instrument [Line Items]
Principal	$ 75,000,000

Notes Payable - Terms (Details)

Notes Payable - Terms (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	May 31, 2018USD ($)trading_dayclass$ / shares	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2020USD ($)$ / shares	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)$ / shares
Debt Instrument [Line Items]
Common stock, par value (in dollars per share) | $ / shares		$ 0.001	$ 0.001		$ 0.001
Carrying amount of equity component		$ 125,700	$ 125,700
Effective percentage		5.70%	5.70%
Payment for debt settlement		$ 900
Debt conversion, converted instrument, amount including cash		172,800
Value of common stock issued to settle convertible senior notes			$ 171,840	$ 0
Debt instrument, liability component		47,100	47,100
Loss on extinguishment of debt		$ (3,200)
Common Class A
Debt Instrument [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.001
Common Class A | Common Stock
Debt Instrument [Line Items]
Equity component from partial settlement of 2023 convertible senior notes (in shares) | shares		715,819
Convertible senior notes, 0.25%, due 2023
Debt Instrument [Line Items]
Threshold trading days | trading_day	20
Consecutive trading period | class	30
Minimum sale price of stock as a percentage of the conversion price	130.00%
Number of consecutive trading days of threshold Notes trading price for conversion eligibility to follow | trading_day	5
Trading price as a percentage of the product of common stock sale price and conversion rate	98.00%
Percentage of principal amount of the Notes		100.00%
Interest rate (as a percent)	0.25%
Carrying amount of equity component	$ 119,400	$ 108,357	108,357		$ 119,435
Debt issuance costs	$ 10,200	5,161	$ 5,161		$ 7,162
Debt settlement, amount		$ 51,000
Convertible senior notes, 0.25%, due 2023 | Common Class A
Debt Instrument [Line Items]
Conversion ratio	14.104
Capped calls
Debt Instrument [Line Items]
Initial strike price (in dollars per share) | $ / shares	$ 70.90

Notes Payable - Net Carrying Am

Notes Payable - Net Carrying Amount (Details) - USD ($)	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Dec. 31, 2019	May 31, 2018
Net carrying amount of the equity component of the Notes
Proceeds allocated to the conversion options (debt discount)	$ 125,700,000		$ 125,700,000
Reacquisition of equity component upon conversion			(114,608,000)	$ 0
Issuance costs	(541,000)	$ (953,000)
Convertible senior notes, 0.25%, due 2023
Net carrying amount of the liability component of the Notes
Principal	498,988,000		498,988,000	549,999,000	$ 550,000,000
Unamortized discount	(61,130,000)		(61,130,000)	(84,647,000)
Unamortized issuance costs	(5,161,000)		(5,161,000)	(7,162,000)	(10,200,000)
Net carrying amount	432,697,000		432,697,000	458,190,000
Net carrying amount of the equity component of the Notes
Proceeds allocated to the conversion options (debt discount)	108,357,000		108,357,000	119,435,000	$ 119,400,000
Issuance costs			(2,819,000)	(2,819,000)
Net carrying amount	$ (9,070,000)		$ (9,070,000)	$ 116,616,000

Notes Payable - Interest Expens

Notes Payable - Interest Expense (Details) - Convertible senior notes, 0.25%, due 2023 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest expense recognized related to the Notes
Contractual interest expense	$ 312	$ 344	$ 1,000	$ 1,032
Amortization of debt issuance costs	476	471	1,444	1,387
Amortization of debt discount	5,600	5,536	16,988	16,302
Total interest expense related to the Notes	$ 6,388	$ 6,351	$ 19,432	$ 18,721

Notes Payable - Capped Calls (D

Notes Payable - Capped Calls (Details) - Capped calls $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2018USD ($)$ / sharesshares
Capped calls
Initial strike price (in dollars per share)	$ 70.90
Initial cap price (in dollars per share)	$ 105.04
Number of shares covered | shares	7,757,158
Net cost to purchase the transactions | $	$ 58.5

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for doubtful accounts
Balance, beginning of period	$ 10,248	$ 4,773	$ 6,287	$ 4,945
Additions	1,312	676	8,472	1,116
Write-offs	(832)	(114)	(4,031)	(726)
Balance, end of period	$ 10,728	$ 5,335	$ 10,728	$ 5,335
Percentage of revenue	2.00%	2.00%	1.00%	1.00%

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Sales Credit Reserve (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Sales credit reserve
Balance, beginning of period	$ 11,531	$ 3,076	$ 6,784	$ 3,015
Additions	12,164	5,861	33,714	11,404
Deductions against reserve	(12,915)	(3,834)	(29,718)	(9,316)
Balance, end of period	$ 10,780	$ 5,103	$ 10,780	$ 5,103
Percentage of revenue	2.00%	2.00%	1.00%	1.00%

Revenue by Geographic Area - Re

Revenue by Geographic Area - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Abstract]
Revenue	$ 447,969	$ 295,066	$ 1,213,686	$ 803,244
United States
Disaggregation of Revenue [Abstract]
Revenue	328,056	210,986	881,984	572,537
International
Disaggregation of Revenue [Abstract]
Revenue	$ 119,913	$ 84,080	$ 331,702	$ 230,707

Revenue by Geographic Area - Pe

Revenue by Geographic Area - Percentage of Revenue by Geographic Area (Details) - Revenue from Contract with Customer Benchmark - Geographic Concentration Risk	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
United States
Risks and Uncertainties [Abstract]
Percentage of revenue (as a percent)	73.00%	72.00%	73.00%	71.00%
International
Risks and Uncertainties [Abstract]
Percentage of revenue (as a percent)	27.00%	28.00%	27.00%	29.00%

Commitments and Contingencies -

Commitments and Contingencies - Other Commitments (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)
Long-term Purchase Commitment [Line Items]
Purchase commitment	$ 28.1	$ 51
Minimum
Long-term Purchase Commitment [Line Items]
Term of lease	1 year	1 year
Maximum
Long-term Purchase Commitment [Line Items]
Term of lease	9 years	9 years
Term of non-cancellable agreement		3 years

Commitments and Contingencies_2

Commitments and Contingencies - Indemnification Agreements (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Indemnification Agreements
Loss Contingencies [Line Items]
Amount accrued	$ 0	$ 0

Commitments and Contingencies_3

Commitments and Contingencies - Other taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Taxes payable, jurisdictional estimate	$ 38,800
Accrued taxes	11,500
Liability for uncertain tax positions	$ 25,300	$ 27,000

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred Stock (Details) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Preferred Stock
Preferred stock, authorized (in shares)	100,000,000	100,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) - $ / shares	Sep. 30, 2020	Dec. 31, 2019	May 31, 2018
Common Stock
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Class A
Common Stock
Common stock, authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, par value (in dollars per share)			$ 0.001
Common stock, issued (in shares)	140,173,591	126,882,172
Common stock, outstanding (in shares)	140,173,591	126,882,172
Common Class B
Common Stock
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	10,729,264	11,530,627
Common stock, outstanding (in shares)	10,729,264	11,530,627

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Shares Reserved (Details) - shares	Sep. 30, 2020	Dec. 31, 2019
Stockholders' Equity
Total (in shares)	47,776,773	46,270,890
2016 Stock Option and Incentive Plan
Stockholders' Equity
Stock-based awards available for grant under 2016 Plan (in shares)	19,275,512	14,957,734
Common Class A
Stockholders' Equity
Class A common stock reserved for Twilio.org (in shares)	729,367	795,673
Class A common stock reserved for the convertible senior notes (in shares)	9,756,346	10,472,165
Stock options issued and outstanding
Stockholders' Equity
Stock options issued and outstanding (in shares)	4,946,920	7,705,848
Nonvested restricted stock units issued and outstanding
Stockholders' Equity
Nonvested restricted stock units issued and outstanding (in shares)	8,026,189	8,490,517
Class A common stock committed under 2016 ESPP
Stockholders' Equity
Stock-based awards available for grant under 2016 Plan (in shares)	5,042,439	3,848,953

Stockholders' Equity - Public E

Stockholders' Equity - Public Equity Offering (Details) $ / shares in Units, $ in Billions	1 Months Ended
	Aug. 31, 2020USD ($)$ / sharesshares
Subsidiary, Sale of Stock [Line Items]
Offering price per share (in dollars per share) | $ / shares	$ 247
Aggregate proceeds from stock offering | $	$ 1.4
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Shares sold in offering (in shares) | shares	5,819,838

Stock-Based Compensation - 2008

Stock-Based Compensation - 2008 Stock Option Plan (Details)	Sep. 30, 2020shares
2008 Stock Option Plan
Stock Based Compensation
Shares available for future issuance (in shares)	0

Stock-Based Compensation - 2016

Stock-Based Compensation - 2016 Stock Option Plan (Details) - shares	Jan. 01, 2020	Jan. 01, 2019	Sep. 30, 2020	Jun. 21, 2016
Stock Based Compensation
Increase in shares available for grant (in shares)	1,384,128	1,000,802
Employee and nonemployee stock options
Stock Based Compensation
Expiration term			10 years
Employee and nonemployee stock options | New Hires
Stock Based Compensation
Vesting period			4 years
Employee and nonemployee stock options | First vesting | New Hires
Stock Based Compensation
Vesting period			1 year
Percentage of vesting rights			25.00%
Nonvested restricted stock units issued and outstanding
Stock Based Compensation
Vesting period			4 years
Nonvested restricted stock units issued and outstanding | First vesting | New Hires
Stock Based Compensation
Vesting period			1 year
Percentage of vesting rights			25.00%
2016 Stock Option and Incentive Plan
Stock Based Compensation
Maximum automatic annual increase as a percentage of outstanding common shares			5.00%
Increase in shares available for grant (in shares)	6,920,640	5,004,011
2016 Stock Option and Incentive Plan | Common Class A
Stock Based Compensation
Shares reserved for issuance (in shares)				11,500,000
2016 Stock Option and Incentive Plan | Employee and nonemployee stock options
Stock Based Compensation
Minimum grant price as a percentage of fair market value per share of the underlying common stock on the date of grant (as a percent)			100.00%

Stock-Based Compensation - 20_2

Stock-Based Compensation - 2016 Employee Stock Purchase Plan (Details) - USD ($) $ in Millions	Jan. 01, 2020	Jan. 01, 2019	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jun. 21, 2016
Stock Based Compensation
Increase in shares available for grant (in shares)	1,384,128	1,000,802
Stock plan offering period						6 months
Unrecognized compensation cost, other than options				$ 1.6		$ 1.6
Weighted-average period (in years)						1 month 6 days
Class A common stock committed under 2016 ESPP
Stock Based Compensation
Maximum automatic annual increase (in shares)				1,800,000		1,800,000
Maximum automatic annual increase as a percentage of outstanding common shares				1.00%		1.00%
Common Class A | Class A common stock committed under 2016 ESPP
Stock Based Compensation
Shares reserved for issuance (in shares)							2,400,000
Discount from market price, offering date (as a percent)						15.00%
Purchase price, percentage of fair market value (as a percent)						85.00%
Shares purchased in period (in shares)				0	0
Common Class A | Class A common stock committed under 2016 ESPP | Forecast
Stock Based Compensation
Shares purchased in period (in shares)			103,374

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Number of options outstanding
Granted (in shares)	0	0
Employee and nonemployee stock options
Number of options outstanding
Outstanding options as of the beginning of the period (in shares)			7,150,848
Granted (in shares)			599,909
Exercised (in shares)			(3,110,685)
Forfeited and cancelled (in shares)			(248,152)
Outstanding options as of the end of the period (in shares)	4,391,920		4,391,920	7,150,848
Weighted- average exercise price (Per share)
Outstanding options as of the beginning of the period (in dollars per share)			$ 28.79
Granted (in dollars per share)			127.74
Exercised (in dollars per share)			20.15
Forfeited and cancelled (in dollars per share)			71.27
Outstanding options as of the end of the period (in dollars per share)	$ 46.02		$ 46.02	$ 28.79
Weighted- average remaining contractual term (In years)
Weighted-average remaining contractual term (in years)			6 years 7 months 9 days	6 years 5 months 19 days
Aggregate intrinsic value	$ 883,089		$ 883,089	$ 511,971
Options vested and exercisable and options vested and expected to vest
Options vested and exercisable - number of options outstanding (in shares)	2,678,454		2,678,454
Options vested and exercisable - weighted-average exercise price (in dollars per share)	$ 19.05		$ 19.05
Options vested and exercisable - weighted-average remaining contractual term			5 years 6 months 14 days
Options vested and exercisable - aggregate intrinsic value	$ 610,799		$ 610,799

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock Options - Additional Information (Details) - Employee and nonemployee stock options - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Stock Based Compensation
Aggregate intrinsic value of stock options exercised	$ 89,808	$ 67,952	$ 496,198	$ 355,776
Total estimated grant date fair value of options vested	$ 12,090	$ 20,959	$ 53,110	$ 62,657
Weighted-average grant date fair value per share of options granted (in dollars per share)	$ 0	$ 0	$ 64.06	$ 58.16

Stock-Based Compensation - Perf

Stock-Based Compensation - Performance-Based Stock Options (Details) $ / shares in Units, $ in Thousands	Feb. 28, 2017USD ($)award$ / sharesshares	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2019shares	Sep. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of options outstanding
Granted (in shares) | shares		0	0
Performance-based stock options
Stock-Based Compensation
Number of distinct awards | award	3
Total grant value | $	$ 5,900
Vesting period upon satisfaction of performance condition	24 months
Number of options outstanding
Outstanding options as of the beginning of the period (in shares) | shares				555,000
Granted (in shares) | shares	555,000			0
Exercised (in shares) | shares				0
Forfeited and cancelled (in shares) | shares				0
Outstanding options as of the end of the period (in shares) | shares		555,000		555,000	555,000
Weighted- average exercise price (Per share)
Outstanding options as of the beginning of the period (in dollars per share)				$ 31.72
Granted (in dollars per share)				0
Exercised (in dollars per share)				0
Forfeited and cancelled (in dollars per share)				0
Outstanding options as of the end of the period (in dollars per share)		$ 31.72		$ 31.72	$ 31.72
Weighted-average remaining contractual term
Weighted-average remaining contractual term (in years)				3 years 4 months 28 days	4 years 1 month 28 days
Aggregate intrinsic value | $		$ 119,530		$ 119,530	$ 36,941
Options vested and exercisable
Options vested and exercisable - number of options outstanding (in shares) | shares		508,749		508,749
Options vested and exercisable - weighted-average exercise price (in dollars per share)		$ 31.72		$ 31.72
Options vested and exercisable - weighted-average remaining contractual term				3 years 4 months 28 days
Options vested and exercisable - aggregate intrinsic value | $		$ 109,569		$ 109,569
$13.48 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 13.48
Derived service period as adjusted	3 years 1 month 6 days
$10.26 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 10.26
Derived service period as adjusted	3 years 10 months 24 days
$8.41 grant date fair value
Stock-Based Compensation
Grant date fair value (in dollars per share)	$ 8.41
Derived service period as adjusted	4 years 4 months 24 days

Stock-Based Compensation - St_3

Stock-Based Compensation - Stock Options - Unrecognized Compensation Cost (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Stock Based Compensation
Weighted-average period (in years)	1 month 6 days
Stock options issued and outstanding
Stock Based Compensation
Unrecognized compensation cost, options	$ 75
Weighted-average period (in years)	2 years 2 months 12 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Units Activity (Details) - Nonvested restricted stock units issued and outstanding - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Number of awards outstanding
Nonvested RSUs at the beginning of the period (in shares)	8,490,517
Granted (in shares)	2,826,569
Vested (in shares)	(2,621,821)
Forfeited and canceled (in shares)	(669,076)
Nonvested RSUs at the end of the period (in shares)	8,026,189
Weighted- average grant date fair value (Per share)
Nonvested RSUs at the beginning of the period (in dollars per share)	$ 74.21
Granted (in dollars per share)	176.19
Vested (in dollars per share)	70.95
Forfeited and canceled (in dollars per share)	88.32
Nonvested RSUs at the end of the period (in dollars per share)	$ 111.58
Aggregate intrinsic value (In thousands)
Aggregate intrinsic value	$ 1,979,215	$ 830,167

Stock-Based Compensation - Re_2

Stock-Based Compensation - Restricted Stock Units - Unrecognized Compensation Cost (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Stock Based Compensation
Unrecognized compensation cost, other than options	$ 1.6
Weighted-average period (in years)	1 month 6 days
Nonvested restricted stock units issued and outstanding
Stock Based Compensation
Unrecognized compensation cost, other than options	$ 818.6
Weighted-average period (in years)	2 years 7 months 6 days

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions (Details) - $ / shares	Feb. 28, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Valuation Assumptions
Options granted (in shares)		0	0
Employee stock options
Valuation Assumptions
Expected term (in years)		0 years	0 years	6 years 29 days
Expected volatility, low end of range (as a percent)				51.90%	48.30%
Expected volatility, high end of range (as a percent)				56.00%	66.50%
Risk-free interest rate, low end of range (as a percent)				0.40%	2.40%
Risk-free interest rate, high end of range (as a percent)				1.40%	2.50%
Dividend rate				0.00%	0.00%
Class A common stock committed under 2016 ESPP
Valuation Assumptions
Expected term (in years)				6 months	6 months
Expected volatility, high end of range (as a percent)				72.10%	50.30%
Risk-free interest rate, high end of range (as a percent)				0.20%	2.40%
Dividend rate				0.00%	0.00%
Performance-based stock options
Valuation Assumptions
Options granted (in shares)	555,000			0
Asset volatility (as a percent)				40.00%
Equity volatility (as a percent)				45.00%
Discount rate (as a percent)				14.00%
Stock price at grant date (in dollars per share)		$ 31.7		$ 31.7
Minimum | Employee stock options
Valuation Assumptions
Fair value of common stock (in dollars per share)				108.4	$ 111.3
Expected term (in years)					3 months 29 days
Maximum | Employee stock options
Valuation Assumptions
Fair value of common stock (in dollars per share)				$ 191.9	$ 130.7
Expected term (in years)					6 years 29 days

Stock-Based Compensation - St_4

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Stock-Based Compensation Expense
Stock-based compensation expense	$ 89,410	$ 68,268	$ 237,822	$ 197,332
Cost of revenue
Stock-Based Compensation Expense
Stock-based compensation expense	2,237	1,674	6,217	5,106
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense	46,294	34,348	119,344	93,388
Sales and marketing
Stock-Based Compensation Expense
Stock-based compensation expense	26,573	16,143	69,602	42,456
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense	$ 14,306	$ 16,103	$ 42,659	$ 56,382

Net Loss per Share Attributab_3

Net Loss per Share Attributable to Common Stockholders - General Information (Details) - Vote	Sep. 30, 2020	Dec. 31, 2019
Common Class A
Net Loss Per Share Attributable to Common Stockholders
Votes per share	1	1
Common Class B
Net Loss Per Share Attributable to Common Stockholders
Votes per share	10	10

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Loss Per Share Attributable to Common Stockholders
Net loss attributable to common stockholders (in thousands)	$ (116,914)	$ (87,734)	$ (311,628)	$ (216,816)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	147,501,075	136,400,739	142,832,021	127,506,529
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.79)	$ (0.64)	$ (2.18)	$ (1.70)

Net Loss Per Share Attributab_5

Net Loss Per Share Attributable to Common Stockholders - Anti-Dilutive Securities (Details) - $ / shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Anti-dilutive securities
Antidilutive securities (in shares)	18,819,665	21,208,559
Conversion price (in dollars per share)	$ 70.90
Stock options issued and outstanding
Anti-dilutive securities
Antidilutive securities (in shares)	4,946,920	8,348,766
Nonvested restricted stock units issued and outstanding
Anti-dilutive securities
Antidilutive securities (in shares)	8,026,189	8,468,680
Class A common stock reserved for Twilio.org
Anti-dilutive securities
Antidilutive securities (in shares)	729,367	776,334
Class A common stock committed under 2016 ESPP
Anti-dilutive securities
Antidilutive securities (in shares)	103,374	99,158
Conversion spread
Anti-dilutive securities
Antidilutive securities (in shares)	5,013,815	3,515,621

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Income tax expense (benefit)	$ 648	$ (2,555)	$ 1,919	$ (56,309)
Release of valuation allowance		2,500		55,200
SendGrid
Business Acquisition [Line Items]
Release of valuation allowance		$ 49,200		$ 49,200

Subsequent Events (Details)

Subsequent Events (Details) - Segment - USD ($) $ in Millions	Oct. 12, 2020	Sep. 30, 2020
Subsequent Events
Acquisition related costs		$ 0.8
Subsequent Events
Subsequent Events
Aggregate consideration	$ 3,200